Method for remediation of polycyclic aromatic hydrocarbon contaminated soil by enhanced microwave

Abstract

This invention discloses a method for enhanced microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, comprising the following steps: S1, soil selection; S2, soil pretreatment; S3, preparation of enhancing agents: the enhancing agents include a first microwave absorber and a second microwave absorber; the first microwave absorber is a biochar microwave absorber; the second microwave absorber includes manganese dioxide, magnetite, persulfate, and self-healing microcapsules doped with sodium dodecyl sulfate with a particle size of 1-3 mm; S4, remediation treatment; the self-healing microcapsules doped with sodium dodecyl sulfate prepared by this invention utilize the gradual release of sodium dodecyl sulfate encapsulated in the microcapsules as the temperature rises, enhancing the desorption efficiency of PAHs from soil particles, resulting in a significant increase in desorption rate; and the acid and alkali resistance of the polydopamine coating distributed on the outer side of the capsule wall adapts to complex soil environments, making the remediation effect more stable.

Description

Technical Field

[0001] This invention relates to the field of soil organic pollution remediation technology, specifically to a method for enhancing microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil. Background Technology

[0002] Microwave heating technology is a process that heats soil both internally and externally simultaneously, rapidly increasing the overall soil temperature and causing pollutants to volatilize, decompose, or become fixed quickly, achieving remediation. While microwave remediation technology for organically contaminated soil has significant advantages in terms of low carbon footprint, environmental friendliness, and safety, several challenges remain. The low dielectric constant of soil particles results in a small dielectric loss tangent, hindering rapid heating of contaminated soil. Furthermore, the outward radiation range of microwaves is limited. Beyond a certain range, heating of contaminated soil in more distant or deeper areas relies solely on heat conduction from nearby or shallower areas, significantly reducing the heating efficiency of contaminated soil in these areas. Therefore, it is not only difficult to further improve the efficiency of pollutant removal from the soil, but it also increases energy consumption, prolongs remediation time, and raises remediation costs.

[0003] Different materials exhibit reflection, absorption, and penetration of microwaves in a microwave field, depending on their dielectric constant, dielectric loss coefficient, shape, and moisture content. The dielectric constant measures a material's ability to prevent microwaves from penetrating it, while the dielectric loss coefficient reflects its ability to dissipate microwaves. At a given frequency, a higher coefficient indicates a lower chance of microwave radiation penetrating, meaning a stronger ability to absorb energy. Materials that absorb microwaves and convert them into heat are called dielectric materials (or microwave absorbers). Given the low energy conversion efficiency and limited remediation range of microwave remediation, certain microwave absorbers can be added to enhance the absorption of microwave energy by contaminated soil. In an electromagnetic field, the absorber is heated first due to its high dielectric or magnetic loss, forming uniform "hot spots" in the contaminated soil. These "hot spots" drive a uniform overall temperature increase in the soil, thereby improving the slow heating of contaminated soil and increasing the microwave remediation range and depth. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for enhancing microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil.

[0005] The technical solution of this invention is: a method for enhancing microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, comprising the following steps:

[0006] S1. Soil Zoning: Soil 0-10m away from the plant area is designated as heavily polluted soil; soil 100-110m away from the plant area is designated as lightly polluted soil.

[0007] S2. Soil pretreatment: Take 50-100g of soil from the heavily polluted area and 50-100g of soil from the lightly polluted area respectively, air dry them naturally, pass them through a 30-40 mesh sieve, and dry them for 2-4 days; then place them in a crucible, add water to control the soil moisture content to 8-10%, and microwave treat them for 10-15 minutes under microwave power of 800-900W.

[0008] S3. Preparation of reinforcing agent: The reinforcing agent includes a first microwave absorber and a second microwave absorber; the first microwave absorber is a biochar microwave absorber; the second microwave absorber, by weight, includes 8-15 parts of manganese dioxide, 1-3 parts of magnetite, 5-7 parts of persulfate and 9-11 parts of self-healing microcapsules with a particle size of 1-3 mm and doped with sodium dodecyl sulfate.

[0009] S4. Contaminated soil remediation:

[0010] For soil in lightly polluted areas: add the biochar microwave absorber to the soil in lightly polluted areas at a ratio of 1-20wt%, mix evenly, and then microwave treat it under a microwave power of 800W for 8-10 minutes. After treatment, cool to obtain the remediated soil.

[0011] For heavily polluted soil: embed the second microwave absorber into the graphene layer, then mix the second microwave absorber with the heavily polluted soil at a ratio of 5-7 wt%, and let it stand for 20-24 hours; for 0-20 mm surface heavily polluted soil: microwave irradiate at a power of 2.5-3.5 kW for 15-20 minutes, heat to 120-150℃ and hold for 30-40 minutes, then cool to 35-45℃ for microbial remediation treatment; for 20-50 mm deep heavily polluted soil: microwave irradiate at a power of 4.5-5.5 kW for 25-30 minutes, heat to 180-200℃ and hold for 20-30 minutes, then cool to 35-45℃ for microbial remediation treatment.

[0012] Furthermore, the method for embedding the second microwave absorbing agent into the graphene layer is as follows: the second microwave absorbing agent is mixed with a graphene oxide suspension at a solid-liquid ratio of 1g:10-12mL, and ultrasonically dispersed at 25-30℃ and 300-400W for 30-40min to form a homogeneous slurry. Then, it is microwave irradiated at a power of 750-850W for 5-8min, and freeze-dried to obtain a composite microwave absorbing material; wherein the MnO2 loading rate is ≥15%, and the microcapsule encapsulation integrity rate is ≥90%.

[0013] Explanation: The interlayer confinement effect of graphene enhances the catalytic activity of MnO2 / Fe3O4, improving the decomposition efficiency of persulfate. The high thermal conductivity of graphene enables precise heat transfer to contaminated soil. Ultrasonic dispersion exfoliates graphene oxide sheets through cavitation, forming a uniformly dispersed nanoscale suspension system. This allows MnO2 and magnetite particles to embed into the interlayer voids of graphene, reducing the interfacial impedance of the composite material and enhancing the electron migration rate in the microwave field. Microwave radiation triggers the in-situ reduction-oxidation reaction between graphene oxide and MnO2, forming chemical bonds (CO-Mn bonds) and increasing the loading rate to ≥15%. It also induces cross-linking and curing of the polydopamine layer on the surface of the microcapsules, achieving a coverage integrity rate of ≥90% and optimizing remediation efficiency.

[0014] Further, the freeze-drying method is as follows: pre-freeze at -50 to -45°C for 18-24 hours, then heat to -40 to -30°C at a rate of 3-5°C / h, and continue drying under vacuum of ≤10Pa for 36-48 hours until the moisture content is ≤2%.

[0015] Explanation: The pre-freezing process can quickly freeze the slurry, reduce the damage of ice crystals to the material pores, and ensure that the slurry is completely solidified. Subsequent sublimation drying can accelerate the sublimation process of ice crystals and gradually increase the temperature to avoid material collapse. It can maintain the three-dimensional channel structure between graphene layers. The interlayer pores of graphene provide a large number of active sites, enhance the loading and adsorption capacity of manganese dioxide catalyst and polycyclic aromatic hydrocarbons, promote the contact efficiency between polycyclic aromatic hydrocarbons and catalysts, and improve the oxidative degradation rate. The control of water content can ensure the long-term storage stability of composite materials.

[0016] Furthermore, the self-healing microcapsule containing sodium dodecyl sulfate comprises a core repair agent, a capsule wall coating the outer layer of the core repair agent, and polydopamine with an average molecular weight of 500-10,000,000 g / mol arranged on the outer surface of the capsule wall.

[0017] The core repair agent comprises paraffin powder, sodium dodecyl sulfate, cement, an expansion agent, and silica fume in a mass ratio of 2.5-3.5:0.5-1.5:4-6:0.5-1.5:0.5-1.5; the core wall material is polyvinyl alcohol.

[0018] Explanation: The adhesive properties of polydopamine optimize the loading stability of MnO2 on the microcapsule surface, increasing the MnO2 loading rate by ≥30%. Furthermore, polydopamine undergoes structural collapse under microwave thermal fields (>80℃), enabling controlled phased release of the remediation agent: Initial rapid response: Paraffin (melting point 45-60℃) in the capsule core melts under microwave heating, releasing sodium dodecyl sulfate (NDS) for rapid penetration of the contaminated interface and improved PAH desorption efficiency; the swelling agent (e.g., CaO) absorbs water and expands, compressing the capsule wall; the physical cross-linking network of the PVA capsule wall generates microcracks due to swelling stress, releasing silica fume as an initial remediation agent; Mid-term controlled release: Polydopamine gradually degrades in alkaline soil environments (pH>8), exposing capsule wall pores and releasing CaO. 2+ It undergoes a chelation reaction with PAHs; long-term slow release: the residual fragments of polydopamine decompose under the action of soil microorganisms, releasing the residual silica fume in the core, and continuously regulating the soil aggregate structure.

[0019] Furthermore, the preparation method of the self-healing microcapsules doped with sodium dodecyl sulfate is as follows:

[0020] 1) Core prefabrication

[0021] Mix paraffin powder, cement, expanding agent, silica fume, and sodium dodecyl sulfate according to the specified proportions, and add water at a water-to-binder volume ratio of 0.3-0.35:1 and stir until uniform to obtain a slurry; use a pressure molding machine with a pressure of 10-15MPa to form the slurry into particles with a diameter of 1-3mm, and dry at 55-65℃ until the moisture content is ≤5%;

[0022] 2) Capsule wall covering

[0023] Polyvinyl alcohol is dissolved in deionized water to form a coating solution with a concentration of 5-10 wt%. Then, the core particles are suspended in a hot air stream at 50-60°C, and the coating solution is atomized and sprayed to form a capsule wall of 10-50 μm, thus obtaining microcapsules.

[0024] 3) Surface finishing

[0025] The surface of the capsule wall was treated with plasma under an Ar atmosphere to form a groove array with a width of 100-200 nm. Then, the microcapsules were immersed in a Tris buffer containing 2-4 mg / mL polydopamine (pH 8.5). The Tris buffer was sonicated at 35-40 kHz for 5-8 min to allow the Tris buffer to penetrate into the grooves. The microcapsules were then subjected to microwave-assisted crosslinking at 280-320 W for 2-4 min. Finally, the microcapsules were washed 3-5 times with deionized water to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power was 45-55 W and the treatment time was 3-7 min.

[0026] Note: Plasma power > 45W ensures trench depth > 50nm, microwave time < 5min avoids excessive cross-linking leading to coating embrittlement; microwave-assisted cross-linking promotes the reaction of catechol groups of polydopamine with hydroxyl groups of polyvinyl alcohol capsule wall to form covalent bonds, improving coating adhesion and anti-swelling properties; plasma treatment creates nanoscale trenches on the surface of polyvinyl alcohol capsule wall, where polydopamine is embedded through capillary action to form a mechanically interlocked structure, improving the coating's anti-peeling ability;

[0027] The embedded nanogrooves in the polydopamine capsule walls can resist soil particle friction, delay primary rupture, and achieve gradient release of the remediation agent. When cracks or pollution concentrations fluctuate in the soil, undamaged microcapsules can release the remediation agent a second time to maintain the remediation effect. The acid and alkali resistance of the polydopamine coating adapts to complex soil environments, avoids premature deactivation of the remediation agent, and the self-healing mechanism can cope with changes in soil mechanical stress (such as wet-dry cycles and freeze-thaw cycles) to ensure long-term remediation capability.

[0028] Furthermore, the expanding agent comprises, by mass percentage: 35-45% calcium oxide, 25-35% magnesium oxide, and the balance tricalcium aluminate, wherein the silica fume has a purity of ≥95%.

[0029] Note: Initial expansion is initiated by CaO, with MgO providing medium- to long-term volume compensation and C3A enhancing crack resistance; adaptable to complex soil pH environments; high-purity silica fume can improve the chemical stability of microcapsules and reduce side reactions with core repair agents such as cement and paraffin.

[0030] Furthermore, the hot air flow rate is 30-50 m³ / h. 3 / h, relative humidity ≤10%, temperature 50-60℃;

[0031] Note: The above temperature is matched to the heat sensitivity of the material to avoid polydopamine denaturation; the above hot air flow rate ensures uniform suspension of particles and optimizes the coating effect; relative humidity ≤10% prevents the coating liquid from curing or clumping prematurely.

[0032] Furthermore, the parameters for atomized spraying are: atomization pressure: 1.0-1.5MPa, spraying speed: 2-5mL / min, spray gun distance: 15-20cm, and nozzle orifice diameter: 0.3-0.5mm;

[0033] Note: Higher pressure results in finer droplets. Excessive spray speed can lead to uneven coating. A reasonable spray gun distance can optimize droplet distribution and drying efficiency.

[0034] Further, in S4, the method of microbial remediation treatment is as follows: white rot fungi are inoculated into a culture medium and pre-cultured at 28-30℃ for 5-7 days to obtain a fungal suspension. The cooled soil and the fungal suspension are mixed at a volume ratio of 1:50-55, and 2-4wt% lignocellulose is added as a nutrient source for the fungi. The soil moisture content is controlled at 25-35%, the pile thickness is ≤30cm, and the soil is cultured in the dark for 14-15 days, during which time the pile is turned and aerated every 40-48 hours. Then, 4-6wt% of calcium dihydrogen phosphate is added to the total amount of the cooled soil, and a citric acid-sodium citrate buffer solution with a total concentration of 0.1-0.3mol / L and a pH of 6.5-7.0 is sprayed simultaneously. The mixture is mixed at a speed of 20-30r / min for 30-50min, and then covered with an impermeable membrane and cured at 25-30℃ for 7-10 days.

[0035] Description: The white rot fungus is YK-624 (commercially available product). Each 1000 mL of liquid culture medium contains 35-45 mL of corn flour extract, 0.43-0.45 g of ammonium tartrate, 0.19-0.21 g of KH₂PO₄, 0.05-0.056 g of MgSO₄·7H₂O, 10.0-10.2 mg of CaCl₂, 0.8-1.2 mL of inorganic solution, 0.4-0.6 mL of vitamin solution, and 0.2 mol of pH 7 HAc-NaAc buffer solution. Its laccase can further degrade residual PAHs. The added calcium dihydrogen phosphate promotes the precipitation of heavy metal phosphates, solidifies heavy metals, and optimizes soil remediation. Turning and aeration increase soil pore oxygen content, enhance aerobic microbial activity, and improve the mineralization rate of PAHs. The geomembrane prevents excessively rapid water evaporation and excessively small moisture content fluctuations, reducing the difficulty of desorption.

[0036] The beneficial effects of this invention are:

[0037] (1) This invention employs specific remediation treatments for lightly polluted and heavily polluted soils, respectively. For lightly polluted areas, biochar is used as a microwave absorber to achieve low-temperature and efficient desorption of PAHs, avoiding high-temperature damage to soil organic matter. For heavily polluted areas, a layered treatment is used: surface layer activates MnO2 for catalytic oxidation, while deep layer triggers persulfate pyrolysis to generate SO4. - • Free radicals enable deep mineralization of PAHs; MnO2 / magnetite loading in the graphene interlayer forms a dielectric-magnetic double-loss network, improving microwave energy conversion efficiency; the three-dimensional porous structure enriches PAH molecules, increasing their probability of contact with active free radicals and optimizing their repair effect.

[0038] (2) The self-healing microcapsules containing sodium dodecyl sulfate prepared by the present invention utilize the sodium dodecyl sulfate encapsulated in the microcapsules to gradually release as the temperature rises, thereby enhancing the desorption efficiency of PAHs from soil particles and significantly improving the desorption rate; the controlled release effect of persulfate can avoid the instantaneous consumption of oxidant and maintain the long-term remediation effect, and the polydopamine embedded in the nanogrooves of the capsule wall can resist soil particle friction, delay the one-time rupture, and realize the gradient release of the remediation agent; when the soil cracks or the concentration of pollution fluctuates, the undamaged microcapsules can release the remediation agent a second time to maintain the remediation effect; and the acid and alkali resistance of the polydopamine coating is adapted to complex soil environments, making the remediation effect more stable.

[0039] (3) This invention achieves the following breakthroughs in strengthening the microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil with manganese dioxide by embedding a second microwave absorber in the graphene layer: the interlayer loading of MnO2 and magnetite forms a three-dimensional conductive network. Under the synergistic effect of graphene increasing dielectric loss and Fe3O4 increasing magnetic loss, the microwave energy conversion efficiency is more than twice that of a single material. Furthermore, the three-dimensional porous structure of graphene with a sheet spacing of ≤1.5nm can preferentially adsorb PAH molecules and enrich them near the active sites of MnO2 through π-π interaction, thereby increasing the contact probability. This solves the bottleneck problems of instantaneous consumption of oxidant and uneven heat distribution in traditional microwave remediation, and provides an efficient solution for the treatment of complex PAH pollution. Detailed Implementation

[0040] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0041] Example 1: A method for enhancing microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, comprising the following steps:

[0042] S1. Soil Zoning: Soil within 10m of the plant area is designated as heavily polluted soil; soil within 100m of the plant area is designated as lightly polluted soil.

[0043] S2. Soil pretreatment: Take 75g of soil from the heavily polluted area and 75g of soil from the lightly polluted area respectively, air dry them naturally, pass them through a 35-mesh sieve, and dry them for 3 days; then place them in a crucible, add water to control the soil moisture content to 9%, and microwave treat them for 13 minutes under microwave power of 850W.

[0044] S3. Preparation of reinforcing agents: The reinforcing agents include a first microwave absorber and a second microwave absorber; the first microwave absorber is a biochar microwave absorber; the second microwave absorber, by weight, includes 12 parts of manganese dioxide, 2 parts of magnetite, 6 parts of persulfate and 10 parts of self-healing microcapsules with a particle size of 2 mm and doped with sodium dodecyl sulfate.

[0045] S4. Contaminated soil remediation:

[0046] For soil in lightly polluted areas: add biochar microwave absorber to the soil in lightly polluted areas at a ratio of 10wt% and mix evenly. Then, microwave treat it under a microwave power of 800W for 9 minutes. After treatment, cool it to obtain the remediated soil.

[0047] For heavily polluted soil: embed the second microwave absorber into the graphene layer, then mix the second microwave absorber with the heavily polluted soil at a ratio of 6wt% and let it stand for 22 hours; for 0-20mm surface heavily polluted soil: microwave irradiate at 3kW for 18 minutes, heat to 135℃ and hold for 35 minutes, then cool to 40℃ for microbial remediation treatment; for 20-50mm deep heavily polluted soil: microwave irradiate at 5kW for 27 minutes, heat to 190℃ and hold for 25 minutes, then cool to 40℃ for microbial remediation treatment.

[0048] The method for embedding the second microwave absorbing agent into the graphene layer is as follows: the second microwave absorbing agent and graphene oxide suspension are mixed at a solid-liquid ratio of 1g:11mL, ultrasonically dispersed at 28℃ and 350W for 35min to form a homogeneous slurry, and then microwave irradiated at 800W for 7min. After freeze-drying, a composite microwave absorbing material is obtained; wherein the MnO2 loading rate is 15% and the microcapsule encapsulation integrity rate is 90%; the freeze-drying method is as follows: pre-freeze at -48℃ for 21h, then heat to -35℃ at a rate of 4℃ / h, and continue drying under a vacuum of 10Pa for 42h until the water content is 2%;

[0049] The self-healing microcapsule containing sodium dodecyl sulfate comprises a core repair agent, a capsule wall coating the core repair agent, and polydopamine with an average molecular weight of 10,000 g / mol arranged on the outer surface of the capsule wall. The core repair agent comprises paraffin powder, sodium dodecyl sulfate, cement, an expanding agent, and silica fume in a mass ratio of 3:1:5:1:1. The capsule wall material is polyvinyl alcohol. The expanding agent comprises 40% calcium oxide, 30% magnesium oxide, and the balance tricalcium aluminate. The silica fume has a purity of 95%.

[0050] The preparation method of self-healing microcapsules doped with sodium dodecyl sulfate is as follows:

[0051] 1) Core prefabrication

[0052] Mix paraffin powder, cement, expanding agent, silica fume, and sodium dodecyl sulfate in a specified ratio, and add water at a water-to-binder volume ratio of 0.33:1 and stir until homogeneous to obtain a slurry; use a pressure molding machine with a pressure of 13MPa to form 2mm diameter particles from the slurry, and dry them at 60℃ until the moisture content is 5%;

[0053] 2) Capsule wall covering

[0054] Polyvinyl alcohol was dissolved in deionized water to form an 8 wt% coating solution. The core particles were then suspended in a 55°C hot air stream, and the coating solution was atomized and sprayed to form a 30 μm capsule wall, thus obtaining microcapsules. The hot air stream flow rate was 40 m³ / h. 3 / h, relative humidity is 10%; the parameters of atomization spraying are: atomization pressure: 1.3MPa, spraying speed: 3mL / min, spray gun distance: 18cm, nozzle orifice diameter: 0.4mm;

[0055] 3) Surface finishing

[0056] A 150 nm wide groove array was formed on the surface of the capsule wall by plasma treatment under an Ar atmosphere. Then, the microcapsules were immersed in Tris buffer containing 3 mg / mL polydopamine (pH 8.5). The Tris buffer was sonicated at 38 kHz for 7 min to allow the Tris buffer to penetrate into the grooves. The microcapsules were then subjected to microwave-assisted crosslinking treatment at 300 W for 3 min. Finally, the microcapsules were washed four times with deionized water to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power was 50 W and the treatment time was 5 min.

[0057] Example 2: Unlike Example 1, in S2, 5g of soil from a heavily polluted area and 5g of soil from a lightly polluted area were taken, air-dried, and passed through a 30-40 mesh sieve for 2 days. Then, the soil was placed in a crucible, water was added to control the soil moisture content to 8%, and microwaved for 10 minutes under a microwave power of 800W.

[0058] Example 3: Unlike Example 1, in S2, 10g of soil from the heavily polluted area and 10g of soil from the lightly polluted area were taken and air-dried naturally, passed through a 30-40 mesh sieve, and dried for 4 days. Then, they were placed in a crucible, water was added to control the soil moisture content to 10%, and microwaved for 15 minutes under a microwave power of 900W.

[0059] Example 4: Unlike Example 1, in S3, the second microwave absorbing agent, by weight, includes 8 parts of manganese dioxide, 1 part of magnetite, 5 parts of persulfate, and 9 parts of self-healing microcapsules doped with sodium dodecyl sulfate with a particle size of 1 mm.

[0060] Example 5: Unlike Example 1, in S3, the second microwave absorbing agent, by weight, includes 15 parts of manganese dioxide, 3 parts of magnetite, 7 parts of persulfate, and 11 parts of self-healing microcapsules with a particle size of 3 mm and doped with sodium dodecyl sulfate.

[0061] Example 6: Unlike Example 1, in S4, for the soil in the lightly polluted area: biochar microwave absorber is added to the soil in the lightly polluted area at a ratio of 1 wt% and mixed evenly. Then, microwave treatment is carried out under the condition of microwave power of 750W for 8 minutes. After treatment, the soil is cooled to obtain the remediated soil.

[0062] For soil in heavily polluted areas: embed the second microwave absorbing agent into the graphene layer, then mix the second microwave absorbing agent evenly with the soil in the heavily polluted area at a ratio of 5wt%, and let it stand for 20 hours; for soil in the 0mm surface layer of heavily polluted areas: microwave irradiate for 15 minutes at a power of 2.5kW, heat to 120℃ and keep warm for 30 minutes, then cool down to 35℃ for microbial remediation treatment; for soil in the 20mm deep layer of heavily polluted areas: microwave irradiate for 25 minutes at a power of 4.5kW, heat to 180℃ and keep warm for 20 minutes, then cool down to 35℃ for microbial remediation treatment.

[0063] Example 7: Unlike Example 1, in S4, for the lightly polluted soil: biochar microwave absorber is added to the lightly polluted soil at a ratio of 20wt% and mixed evenly. Then, microwave treatment is performed under a microwave power of 850W for 10 minutes. After treatment, the soil is cooled to obtain the remediated soil.

[0064] For soil in heavily polluted areas: embed the second microwave absorber into the graphene layer, then mix the second microwave absorber with the soil in the heavily polluted area at a ratio of 7wt%, and let it stand for 24 hours; for soil in the 20mm surface layer of heavily polluted areas: microwave irradiate at a power of 3.5kW for 20 minutes, heat to 150℃ and keep warm for 40 minutes, then cool down to 45℃ for microbial remediation treatment; for soil in the 50mm deep layer of heavily polluted areas: microwave irradiate at a power of 5.5kW for 30 minutes, heat to 200℃ and keep warm for 30 minutes, then cool down to 45℃ for microbial remediation treatment.

[0065] Example 8: Unlike Example 1, the method of embedding the second microwave absorbing agent into the graphene layer is as follows: the second microwave absorbing agent and graphene oxide suspension are mixed at a solid-liquid ratio of 1g:10mL, ultrasonically dispersed at 25℃ and 300W for 30min to form a homogeneous slurry, then microwave irradiated at 750W for 5min, and freeze-dried to obtain the composite microwave absorbing material.

[0066] Example 9: Unlike Example 1, the method of embedding the second microwave absorbing agent into the graphene layer is as follows: the second microwave absorbing agent and graphene oxide suspension are mixed at a solid-liquid ratio of 1g:12mL, ultrasonically dispersed at 30℃ and 400W for 40min to form a homogeneous slurry, and then microwave irradiated at 850W for 8min. After freeze-drying, a composite microwave absorbing material is obtained.

[0067] Example 10: Unlike Example 1, the freeze-drying method is as follows: pre-freeze at -50°C for 18 hours, then heat to -40°C at a rate of 3°C / h, and continue drying under a vacuum of 10 Pa for 36 hours until the moisture content is 2%.

[0068] Example 11: Unlike Example 1, the freeze-drying method is as follows: pre-freeze at -45°C for 24 hours, then heat to -30°C at a rate of 5°C / h, and continue drying under a vacuum of 10Pa for 48 hours until the moisture content is 2%.

[0069] Example 12: Unlike Example 1, the core repair agent includes paraffin powder, sodium dodecyl sulfate, cement, expansion agent, and silica fume in a mass ratio of 2.5:0.5:4:0.5:0.5.

[0070] Example 13: Unlike Example 1, the core repair agent includes paraffin powder, sodium dodecyl sulfate, cement, expansion agent, and silica fume in a mass ratio of 3.5:1.5:6:1.5:1.5.

[0071] Example 14: Unlike Example 1, the expanding agent, by mass percentage, comprises: 35% calcium oxide, 25% magnesium oxide, and the balance tricalcium aluminate, and the silica fume has a purity of 97%.

[0072] Example 15: Unlike Example 1, the expanding agent, by mass percentage, comprises: 45% calcium oxide, 35% magnesium oxide, and the balance tricalcium aluminate, with silica fume purity of 95%.

[0073] Example 16: Unlike Example 1, paraffin powder, cement, expanding agent, silica fume, and sodium dodecyl sulfate were mixed in proportion, and water was added at a water-to-binder volume ratio of 0.3:1 and stirred until uniform to obtain a slurry; the slurry was made into 1 mm diameter particles using a pressure molding machine with a pressure of 10 MPa and dried at 55°C until the moisture content was 5%.

[0074] Example 17: Unlike Example 1, paraffin powder, cement, expanding agent, silica fume, and sodium dodecyl sulfate were mixed in proportion, and water was added at a water-to-binder volume ratio of 0.35:1 and stirred until uniform to obtain a slurry; the slurry was made into granules with a diameter of 3 mm using a pressure molding machine with a pressure of 15 MPa, and dried at 65°C until the moisture content was 5%.

[0075] Example 18: Unlike Example 1, polyvinyl alcohol was dissolved in deionized water to form a 5 wt% coating solution. The core particles were then suspended in a 50°C hot air stream, and the coating solution was atomized and sprayed to form a 10 μm capsule wall, thus obtaining microcapsules. The hot air stream flow rate was 30 m³ / h. 3 / h, relative humidity is 10%; the parameters for atomized spraying are: atomization pressure: 1.0MPa, spraying speed: 2mL / min, spray gun distance: 15cm, nozzle orifice diameter: 0.3mm.

[0076] Example 19: Unlike Example 1, polyvinyl alcohol was dissolved in deionized water to form a 10 wt% coating solution. The core particles were then suspended in a 60°C hot air stream, and the coating solution was atomized and sprayed to form a 50 μm capsule wall, thus obtaining microcapsules. The hot air stream flow rate was 50 m³ / h. 3 / h, relative humidity is 10%; the parameters for atomized spraying are: atomization pressure: 1.5MPa, spraying speed: 5mL / min, spray gun distance: 20cm, nozzle orifice diameter: 0.5mm.

[0077] Example 20: Unlike Example 1, a 100 nm wide groove array was formed on the surface of the capsule wall by plasma treatment under an Ar atmosphere. Then, the microcapsules were immersed in Tris buffer containing 2 mg / mL polydopamine (pH = 8.5), and ultrasonic treatment was performed at 35 kHz for 5 min to allow the Tris buffer to penetrate into the grooves. Microwave crosslinking treatment was performed at 280 W for 2 min. Finally, the microcapsules were washed three times with deionized water to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power was 45 W and the treatment time was 3 min.

[0078] Example 21: Unlike Example 1, a 200 nm wide groove array was formed on the surface of the capsule wall by plasma treatment under an Ar atmosphere. Then, the microcapsules were immersed in Tris buffer containing 4 mg / mL polydopamine (pH = 8.5), and ultrasonically assisted at 40 kHz for 8 min to allow the Tris buffer to penetrate into the grooves. Microwave crosslinking was then performed at 320 W for 4 min. Finally, the capsules were washed 5 times with deionized water to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power was 55 W and the treatment time was 7 min.

[0079] Example 22: Unlike Example 1, in S4, the microbial remediation treatment method is as follows: White rot fungi are inoculated into the culture medium and pre-cultured at 29°C for 6 days to obtain a fungal suspension. The cooled soil and the fungal suspension are mixed at a volume ratio of 1:53, and 3wt% lignocellulose is added. The soil moisture content is controlled at 30%, and the pile is piled up to a thickness of 30cm. It is then cultured in the dark for 14 days, during which time the pile is turned and aerated every 44 hours. Then, 5wt% of calcium dihydrogen phosphate is added to the total amount of cooled soil, and a 0.2mol / L citric acid-sodium citrate buffer solution with a pH of 6.8 is sprayed simultaneously. The mixture is mixed at 25r / min for 40min, and then covered with an impermeable membrane and cured at 27°C for 8 days.

[0080] Example 23: Unlike Example 22, in the microbial remediation treatment method, white rot fungi are inoculated into the culture medium and pre-cultured at 28°C for 5 days to obtain a fungal suspension. The cooled soil is mixed with the fungal suspension at a volume ratio of 1:50, and 2wt% lignocellulose is added. The soil moisture content is controlled at 25%, the pile thickness is 25cm, and it is cultured in the dark for 14 days, during which time the pile is turned and aerated every 40 hours.

[0081] Example 24: Unlike Example 22, in the microbial remediation treatment method, white rot fungi are inoculated into the culture medium and pre-cultured at 30°C for 7 days to obtain a fungal suspension. The cooled soil is mixed with the fungal suspension at a volume ratio of 1:55, and 4wt% lignocellulose is added. The soil moisture content is controlled at 35%, the pile thickness is 30cm, and it is cultured in the dark for 15 days, during which time the pile is turned and aerated every 48 hours.

[0082] Example 25: Unlike Example 22, in the microbial remediation treatment method, 4 wt% of calcium dihydrogen phosphate was added to the total amount of soil after cooling, and a 0.1 mol / L citric acid-sodium citrate buffer solution with pH=6.5 was sprayed simultaneously. The mixture was stirred at 20 r / min for 30 min, and then covered with an impermeable membrane and cured at 25°C for 7 days.

[0083] Example 26: Unlike Example 22, in the microbial remediation method, 6 wt% of calcium dihydrogen phosphate was added to the total amount of soil after cooling, and a 0.3 mol / L citric acid-sodium citrate buffer solution with a pH of 7.0 was sprayed simultaneously. The mixture was stirred at 30 r / min for 50 min, and then covered with an impermeable membrane and cured at 30°C for 10 days.

[0084] Experimental Example: The actual contaminated soil was yellow-brown soil. The types and concentrations of pollutants are shown in Table 1. Soil within 0-10m of the plant area was designated as heavily polluted, with a total PAH concentration of 206.63 mg / kg; soil within 100-110m of the plant area was designated as lightly polluted, with a total PAH concentration of 96.8 mg / kg. The polycyclic aromatic hydrocarbons (PAHs) in this plant area were mainly tricyclic and tetracyclic. The concentrations of fluorene and pyrene in the lightly polluted soil were similar to those in the heavily polluted soil, and the concentration of benzo[g,h,i]perylene in the lightly polluted soil was higher than that in the heavily polluted soil, indicating that these three pollutants have the ability to migrate over long distances.

[0085] Table 1. PAH content in soil of an aromatics plant

[0086]

[0087] The degradation rates of PAHs in lightly polluted and heavily polluted soils after treatment in Examples 1-26 and Comparative Examples 1-6 were measured, and the average value was recorded as the PAHs degradation rate on the day of treatment. The degradation fluctuation rate of lightly polluted soils at 30 and 60 days after treatment, and the degradation fluctuation rate of heavily polluted soils at 60 and 90 days after treatment were measured.

[0088] The method for determining PAHs in soil is as follows:

[0089] HPLC / UV determination conditions: Shimadzu LC-20AT liquid chromatography, 5 μm, 4.6 mm × 150 mm alkyl C18 reversed-phase column, mobile phase: chromatographic grade acetonitrile, flow rate: 1.0 mL / min, column temperature: 40 °C, injection volume: 20 μL, detection wavelength: 245 nm. Acetonitrile-water gradient elution method was used: 0-27.00 min acetonitrile 65%, water 35%; 27.00-45.00 min acetonitrile 100%; 45.00-51.00 min acetonitrile 100%; 51.00-56.00 min acetonitrile 65%, water 35%; 56.00-60.00 min acetonitrile 65%, water 35%.

[0090] 1. The effect of microwave pretreatment on the degradation rate of PAHs in contaminated soil was investigated. The results are shown in Table 2.

[0091] Meanwhile, Comparative Example 1 was set up. The difference between Comparative Example 1 and Example 1 is that the soil was not microwave-treated.

[0092] Table 2 shows the effects of Examples 1-3 and Comparative Example 1 on the PAHs degradation rate of soil in the contaminated area.

[0093]

[0094] Conclusion: Compared with Comparative Example 1, Examples 1-3 show that the lack of microwave pretreatment of soil in Comparative Example 1 resulted in a decrease in the degradation rate of PAHs in the contaminated soil. In Examples 1-3, the degradation fluctuation rate of soil in lightly polluted areas was ≤5% at 30 and 60 days compared to day 1, and the degradation fluctuation rate of soil in heavily polluted areas was also ≤9% at 60 and 90 days compared to day 1. This is because microwave pretreatment can activate the heat generation of the microwave absorber, raising its temperature to 50-60℃, promoting the metabolic activity of functional bacteria (such as Pseudomonas), shortening the degradation cycle of PAHs and increasing the degradation rate.

[0095] 2. Investigate the effect of the method of adding the second absorber on the degradation rate of PAHs in the contaminated soil.

[0096] Comparative Example 2 and Comparative Example 3 were also set up, and the results are shown in Table 3.

[0097] Comparative Example 2: Unlike Example 1, the second absorbing agent was not embedded in the graphene layer and was processed directly.

[0098] Comparative Example 3: Unlike Example 1, the freeze-drying method was to directly dry at -48°C until the moisture content was 2%.

[0099] Table 3. Effects of Examples 1, 6-11, and Comparative Examples 2-3 on PAHs degradation rate in contaminated soil.

[0100]

[0101] Conclusion: Comparing Examples 1, 6-9, and Comparative Example 2, it can be concluded that in Comparative Example 2, directly treating the soil without embedding the second microwave absorber in the graphene layer significantly affected the degradation rate of PAHs in the contaminated area and the degradation fluctuations at 30 and 60 days in the lightly polluted area, and at 60 and 90 days in the heavily polluted area. This is mainly because when the second microwave absorber is directly mixed, manganese dioxide and magnetite tend to agglomerate due to the lack of graphene fixation, leading to a decrease in microwave absorption efficiency and a reduction in the effective contact area for the release of free radicals by persulfates (such as potassium persulfate). This results in loss of dispersibility and activity; microcapsules without embedded graphene layers may rupture prematurely under high temperature and microwave conditions (especially during deep treatment at 190℃), leading to premature release of sodium dodecyl sulfate. Excessive local concentration may inhibit subsequent oxidation reactions, and self-healing microcapsules are at risk of failure; furthermore, without embedded graphene, the microwave absorber is easily affected by soil organic matter adsorption or water migration, resulting in uneven distribution of the oxidant (persulfate). After rapid initial degradation, the active components are depleted, and later rebound or degradation stagnation occurs, thus increasing the degradation fluctuation of heavily polluted soil to 10-15%.

[0102] Comparing Examples 1, 10-11, and Comparative Example 3, it can be concluded that freeze-drying in Comparative Example 3, specifically drying directly at -48℃ to a moisture content of 2%, significantly affects the degradation rate of PAHs in the contaminated soil, as well as the degradation fluctuations over 30 and 60 days in lightly polluted areas and over 90 days in heavily polluted areas. This is mainly because staged freeze-drying, by controlling the heating rate, forms a uniform porous structure, increasing the specific surface area by approximately 35-40%, which helps enhance the contact activity between the microwave absorber (manganese dioxide, magnetite) and the pollutants. Direct freeze-drying, due to rapid freezing, results in uneven pore distribution and limited specific surface area. Furthermore, direct drying leads to microwave absorber aggregation, reduced microwave absorption efficiency, decreased free radical generation, and insufficient PAH oxidation reaction. Direct drying also causes premature microcapsule rupture, rapid initial release of SDS, depletion of activity in the later stages, deactivation of the microwave absorber, and secondary release of high-cyclic PAHs, thereby increasing the degradation fluctuations of contaminated soil in both lightly and heavily polluted areas. Considering all factors, the scheme in Example 1 of this application is optimal.

[0103] 3. Investigate the effects of self-healing microcapsules containing sodium dodecyl sulfate and their preparation methods on the degradation rate of PAHs in contaminated soil.

[0104] Comparative examples 4, 5, and 6 were also set up, and the results are shown in Table 4.

[0105] Comparative Example 4: Unlike Example 1, the second absorber does not contain self-healing microcapsules containing sodium dodecyl sulfate.

[0106] Comparative Example 5: Unlike Example 1, the self-healing microcapsules doped with sodium dodecyl sulfate do not have polydopamine arranged on their surface.

[0107] Comparative Example 6: Unlike Example 1, polydopamine was directly coated onto the surface of the capsule wall.

[0108] Table 4. Effects of Examples 1, 4-5, 12-21, and Comparative Examples 4-6 on PAHs degradation rate in contaminated soil.

[0109]

[0110] Conclusion: Comparison of Examples 1, 4-5, and Comparative Example 4 shows that the self-healing microcapsules without sodium dodecyl sulfate in the second microwave absorber have a significant impact on the degradation rate of PAHs in the contaminated soil and the degradation fluctuations at 30 and 60 days in the lightly polluted area and at 60 and 90 days in the heavily polluted area. This is mainly because after removing the microcapsules, sodium dodecyl sulfate (SDS) cannot be released with the microwave treatment gradient, resulting in a decrease in the activation efficiency of persulfate in the soil and a decrease in the initial degradation rate; and it also exacerbates the degradation fluctuation rate.

[0111] Comparisons of Examples 1, 12-21, and Comparative Examples 5 and 6 show that the self-healing microcapsules doped with sodium dodecyl sulfate, whether without polydopamine on the surface or directly coated with polydopamine, significantly affect the degradation rate of PAHs in contaminated soil and the degradation fluctuations over 30 and 60 days in lightly polluted areas and over 60 and 90 days in heavily polluted areas. This is mainly because the adhesion of polydopamine optimizes the loading stability of MnO2 on the surface of the microcapsules, increasing the MnO2 loading rate by ≥30%. Furthermore, polydopamine undergoes structural collapse under microwave thermal field (>80℃), which can control the phased release of the remediation agent, achieve sustainable release of the second microwave absorber, and optimize the degradation rate of PAHs and the degradation fluctuation over time.

[0112] In Comparative Example 6, the directly coated polydopamine layer lacked trench anchoring, resulting in a 2-3 times higher SDS release rate. This led to excessive initial activation and consumption of the oxidant (persulfate), a decrease in PAH degradation rate, and a decrease in the mechanical strength of the unreinforced polydopamine layer under microwave radiation. This increased the rupture rate of microcapsules in deep soil treatment and significantly increased the risk of secondary release of high-cyclic PAHs (such as benzo[a]pyrene). Direct coating resulted in localized enrichment of SDS in the soil, with a vigorous initial oxidation reaction but insufficient activity in the later stages, leading to a rebound in the residual concentration of PAHs. Considering all factors, Example 1 was the optimal solution.

[0113] 4. The effects of post-treatment methods on the degradation rate of PAHs in the contaminated soil were investigated. The results are shown in Table 5.

[0114] Table 5. Effects of Examples 1, 22-26 on PAHs degradation rate in contaminated soil.

[0115]

[0116] Conclusion: A comparison of Examples 1 and 22-26 shows that the post-treatment in Examples 22-26 significantly improved the degradation rate of PAHs in the polluted soil, as well as the degradation fluctuations over 30 and 60 days in lightly polluted areas and over 60 and 90 days in heavily polluted areas. In Example 1, without inoculation with white-rot fungi, enzyme systems (such as lignin peroxidase) were unable to continuously degrade insoluble PAHs, leading to re-adsorption of residual pollutants. The absence of calcium dihydrogen phosphate resulted in increased free Fe in the soil. 2+ The reduced content of benzo[a]pyrene inhibits persulfate activation and decreases the degradation rate of benzo[a]pyrene. The absence of citrate buffer leads to a soil pH increase above 8.5, causing nano-manganese dioxide (MnO2) to aggregate and become inactive, thus reducing the oxidation efficiency of high-cyclic PAHs. Laccase from white-rot fungi can continue to degrade residual PAHs, and the added calcium dihydrogen phosphate promotes the precipitation of heavy metal phosphates, solidifies heavy metals, and optimizes soil remediation. White-rot fungi and persulfate can synergistically decompose high-cyclic PAHs. When post-treatment is lacking, the half-life of benzo[a]pyrene in deep soil is prolonged, resulting in a decrease in PAH degradation capacity. Considering all factors, Example 22 is selected as the optimal solution.

Claims

1. A method for enhancing microwave remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, characterized in that, Includes the following steps: S1. Soil Zoning: Soil within 0-10 m of the plant area is designated as heavily polluted soil; soil within 100-110 m of the plant area is designated as lightly polluted soil. S2. Soil pretreatment: Take 50-100g of soil from the heavily polluted area and 50-100g of soil from the lightly polluted area respectively, air dry them naturally, pass them through a 30-40 mesh sieve, and dry them for 2-4 days; then place them in a crucible, add water to control the soil moisture content to 8-10%, and microwave treat them for 10-15 minutes under microwave power of 800-900W. S3. Preparation of reinforcing agent: The reinforcing agent includes a first microwave absorber and a second microwave absorber; the first microwave absorber is a biochar microwave absorber; the second microwave absorber, by weight, includes 8-15 parts of manganese dioxide, 1-3 parts of magnetite, 5-7 parts of persulfate and 9-11 parts of self-healing microcapsules with a particle size of 1-3 mm and doped with sodium dodecyl sulfate. S4. Contaminated soil remediation: For soil in lightly polluted areas: add the biochar microwave absorber to the soil in lightly polluted areas at a ratio of 1-20wt% and mix evenly. Then, microwave treat it under a microwave power of 750-850W for 8-10 minutes. After treatment, cool it to obtain the remediated soil. For soil in heavily polluted areas: embed the second microwave absorber into the graphene layer, then mix the second microwave absorber with the soil in the heavily polluted area at a ratio of 5-7wt%, and let it stand for 20-24 hours; for soil in heavily polluted areas with a surface layer of 0-20mm: microwave irradiate at a power of 2.5-3.5kW for 15-20 minutes, heat to 120-150℃ and keep warm for 30-40 minutes, then cool down to 35-45℃ for microbial remediation treatment; For soil in heavily polluted areas with a depth of 20-50mm: microwave radiation at a power of 4.5-5.5kW for 25-30 minutes, heat to 180-200℃ and hold for 20-30 minutes, then cool to 35-45℃ for microbial remediation treatment; The self-healing microcapsule containing sodium dodecyl sulfate includes a core repair agent, a capsule wall covering the outer layer of the core repair agent, and polydopamine with an average molecular weight of 500-10,000,000 g / mol arranged on the outer surface of the capsule wall. The core repair agent comprises paraffin powder, sodium dodecyl sulfate, cement, an expansion agent, and silica fume in a mass ratio of 2.5-3.5:0.5-1.5:4-6:0.5-1.5:0.5-1.5; the core wall material is polyvinyl alcohol. The preparation method of the self-healing microcapsules doped with sodium dodecyl sulfate is as follows: 1) Core prefabrication Mix paraffin powder, cement, expanding agent, silica fume, and sodium dodecyl sulfate according to the specified proportions, and add water at a water-to-binder volume ratio of 0.3-0.35:1, stirring until homogeneous to obtain a slurry; use a pressure molding machine with a pressure of 10-15 MPa to form the slurry into particles with a diameter of 1-3 mm, and dry at 55-65℃ until the moisture content is ≤5%; 2) Capsule wall covering Polyvinyl alcohol is dissolved in deionized water to form a coating solution with a concentration of 5-10 wt%. Then, the core particles are suspended in a hot air stream at 50-60°C, and the coating solution is atomized and sprayed to form a capsule wall of 10-50 μm, thus obtaining microcapsules. 3) Surface finishing The surface of the capsule wall was treated with plasma under an Ar atmosphere to form a groove array with a width of 100-200 nm. Then, the microcapsules were immersed in a Tris buffer containing 2-4 mg / mL polydopamine, with the pH of the Tris buffer being 8.

5. The microcapsules were then treated with ultrasound at 35-40 kHz for 5-8 min to allow the Tris buffer to penetrate into the grooves. The microcapsules were then treated with microwave crosslinking at 280-320 W for 2-4 min. Finally, the microcapsules were washed with deionized water 3-5 times to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power was 45-55 W and the treatment time was 3-7 min.

2. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbon contaminated soil as described in claim 1, characterized in that, The method for embedding the second microwave absorbing agent into the graphene layer is as follows: the second microwave absorbing agent and graphene oxide suspension are mixed at a solid-liquid ratio of 1g:10-12mL, ultrasonically dispersed at 25-30℃ and 300-400W for 30-40min to form a homogeneous slurry, and then microwave irradiated at a power of 750-850W for 5-8min, and freeze-dried to obtain the composite microwave absorbing material.

3. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbon contaminated soil as described in claim 2, characterized in that, The freeze-drying method is as follows: pre-freeze at -50 to -45℃ for 18-24h, then heat to -40 to -30℃ at a rate of 3-5℃ / h, and continue drying under vacuum of ≤10Pa for 36-48h until the moisture content is ≤2%.

4. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbon contaminated soil as described in claim 1, characterized in that, The expanding agent, by mass percentage, comprises: 35-45% calcium oxide, 25-35% magnesium oxide, and the balance tricalcium aluminate, wherein the silica fume has a purity of ≥95%.

5. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbon contaminated soil as described in claim 1, characterized in that, The hot air flow rate is 30-50 m³ / h. 3 / h, relative humidity ≤10%, temperature 50-60℃.

6. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbon contaminated soil as described in claim 1, characterized in that, The parameters for atomized spraying are: Atomization pressure: 1.0-1.5MPa, spray speed: 2-5 mL / min, spray gun distance: 15-20 cm, nozzle orifice diameter: 0.3-0.5 mm.

7. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbon contaminated soil as described in claim 1, characterized in that, In S4, the microbial remediation treatment method is as follows: White rot fungi are inoculated into a culture medium and pre-cultured at 28-30℃ for 5-7 days to obtain a fungal suspension. The cooled soil is mixed with the fungal suspension at a volume ratio of 1:50-55, and 2-4wt% lignocellulose is added. The soil moisture content is controlled at 25-35%, and the pile thickness is ≤30cm. The soil is cultured in the dark for 14-15 days, during which time the pile is turned and aerated every 40-48 hours. Then, 4-6wt% of calcium dihydrogen phosphate is added to the total amount of the cooled soil, and a citric acid-sodium citrate buffer solution with a total concentration of 0.1-0.3mol / L and a pH of 6.5-7.0 is sprayed simultaneously. The mixture is mixed at a speed of 20-30r / min for 30-50min, and then covered with an impermeable membrane and cured at 25-30℃ for 7-10 days.

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