Method for reinforcing microwave remediation of polycyclic aromatic hydrocarbon contaminated soil

Abstract

The invention discloses a method for reinforcing microwave remediation of polycyclic aromatic hydrocarbon contaminated soil. The method comprises the following steps: S1, soil selection; s2, soil pretreatment; s3, preparing an enhancer, wherein the enhancer comprises a first wave-absorbing agent and a second wave-absorbing agent; the first wave absorbing agent is a biochar wave absorbing agent; the second wave absorbing agent comprises manganese dioxide, magnetite, persulfate and a self-repairing microcapsule doped with lauryl sodium sulfate, and the particle size of the self-repairing microcapsule is 1-3mm; s4, repairing treatment is carried out; according to the prepared self-repairing microcapsule internally doped with lauryl sodium sulfate, the lauryl sodium sulfate coated with the microcapsule is gradually released along with temperature rise, the desorption efficiency of PAHs from soil particles is enhanced, and the desorption rate is obviously increased; and the acid and alkali resistance characteristic of the polydopamine coating distributed on the outer side of the capsule wall adapts to the complex soil environment, and the remediation effect is more stable.

Description

Technical Field

[0001] The present invention relates to the technical field of soil organic matter pollution remediation, and in particular to a method for enhancing microwave remediation of polycyclic aromatic hydrocarbons-contaminated soil. Background Art

[0002] Microwave heating technology is a process that heats the soil both internally and externally, rapidly raising the overall temperature of the soil and causing pollutants to volatilize, decompose, or become fixed, achieving the desired treatment effect. Although microwave remediation of organically contaminated soil offers significant advantages in terms of low carbon emissions, environmental friendliness, and safety, numerous challenges remain during the remediation process. Due to the low dielectric constant of soil particles, their dielectric loss tangent is small, hindering the rapid warming of contaminated soil. Microwaves have a limited outward radiation energy range. When this range is exceeded, the temperature of contaminated soil farther or deeper can only be raised by heat conduction from the hotter contaminated soil closer or shallower, significantly reducing the temperature rise of contaminated soil farther or deeper. Therefore, further improving the pollutant removal efficiency in the soil is not only difficult, but also increases the energy consumption of the remediation process, prolongs the remediation time, and increases the remediation cost.

[0003] Different materials reflect, absorb, and transmit microwaves in a microwave field, depending on their properties, such as the 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 certain frequency, the larger the coefficient, the less likely microwave radiation is to penetrate it, meaning the greater the energy absorption capacity. Materials that absorb microwaves and convert them into heat are called dielectric materials (or absorbers). Given the low energy conversion efficiency and limited remediation range of microwave remediation, the addition of certain absorbers can enhance the absorption of microwave energy by contaminated soil. Absorbers are heated first in the electromagnetic field due to their high dielectric or magnetic loss, forming uniform "hot spots" within the contaminated soil. These hot spots promote uniform heating of the soil overall, thereby improving the slow heating rate of contaminated soil and increasing the range and depth of microwave remediation. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for enhancing microwave remediation of polycyclic aromatic hydrocarbons contaminated soil.

[0005] The technical solution of the present invention is: a method for enhancing microwave remediation of polycyclic aromatic hydrocarbons contaminated soil, comprising the following steps:

[0006] S1. Soil zoning: The soil within 0-10m from the plant is considered as the heavily polluted area; the soil within 100-110m from the plant is considered as the lightly polluted area;

[0007] S2. Soil pretreatment: 50-100 g of soil from a heavily polluted area and 50-100 g of soil from a lightly polluted area were taken, air-dried, passed through a 30-40 mesh sieve, and dried for 2-4 days. The soil was then placed in a crucible, water was added to control the soil moisture content to 8-10%, and microwaved at a microwave power of 800-900 W for 10-15 min.

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

[0009] S4. Remediation of contaminated soil:

[0010] For lightly polluted soil: add the biochar absorber to the lightly polluted soil at a ratio of 1-20 wt% and mix evenly, then microwave treat the soil at a microwave power of 800 W for 8-10 minutes, and cool the soil after treatment to obtain the repaired soil;

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

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

[0013] Description: The confinement effect between graphene layers enhances the catalytic activity of MnO2 / Fe3O4 and the decomposition efficiency of persulfate. The high thermal conductivity of graphene enables the precise transfer of heat energy to contaminated soil. Ultrasonic dispersion peels off the graphene oxide sheets through the cavitation effect to form a uniformly dispersed nanoscale suspension system, so that MnO2 and magnetite particles are embedded in the gaps between graphene layers, reducing the interface impedance of the composite material and enhancing the electron migration rate in the microwave field. Microwave radiation triggers the in-situ reduction-oxidation reaction of graphene oxide and MnO2 to form a chemical bond (CO-Mn bond), and the loading rate is increased to ≥15%. It induces the cross-linking and curing of the polydopamine layer on the surface of the microcapsule, with a coating integrity rate of ≥90%, optimizing the repair efficiency.

[0014] Furthermore, the freeze-drying method is: pre-freezing at -50 to -45°C for 18-24 hours, then heating to -40 to -30°C at a rate of 3-5°C / h, and continuously drying for 36-48 hours under a vacuum degree of ≤10Pa until the moisture content is ≤2%;

[0015] Description: The pre-freezing process can quickly freeze the slurry, reduce the damage of ice crystals to the pores of the material, and ensure that the slurry is completely solidified. The subsequent sublimation drying can accelerate the sublimation process of ice crystals and gradually increase the temperature to avoid material collapse; it plays a role in maintaining the three-dimensional pore structure between graphene layers. The pores between graphene layers provide a large number of active sites, enhance the loading and adsorption capacity of manganese dioxide catalysts and polycyclic aromatic hydrocarbons, promote the contact efficiency between polycyclic aromatic hydrocarbons and catalysts, and increase the oxidative degradation rate; moisture content control can ensure the long-term storage stability of the composite material.

[0016] Furthermore, the self-repairing microcapsule doped with sodium lauryl sulfate comprises a core repair agent, a capsule wall coated on the outer layer of the core repair agent, and polydopamine with an average molecular weight of 500-10,000,000 g / mole arranged on the outer surface of the capsule wall;

[0017] The capsule core repair agent includes paraffin powder, sodium lauryl sulfate, cement, 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 capsule wall material is polyvinyl alcohol;

[0018] Description: The adhesion of polydopamine optimizes the loading stability of MnO2 on the surface of microcapsules, making the MnO2 loading rate increase by ≥30%, and the structure of polydopamine collapses under the microwave thermal field (>80℃), which can control the release of the repair agent in stages: Initial rapid response: The paraffin wax (melting point 45-60℃) in the capsule core melts under microwave heating, releasing sodium dodecyl sulfate to quickly penetrate the contaminated interface and improve the desorption efficiency of PAHs; the swelling agent (such as CaO) absorbs water and expands to squeeze the capsule wall, and the physical cross-linked network of the PVA capsule wall produces microcracks due to swelling stress, releasing silica fume as the initial repair agent; Medium-term controlled release: Polydopamine gradually degrades in an alkaline soil environment (pH>8), exposing the pores of the capsule wall and releasing Ca 2+ Chelating reaction with PAHs; long-term sustained release: the residual fragments of polydopamine are decomposed by soil microorganisms, releasing the residual silica fume in the capsule core and continuously regulating the soil aggregate structure.

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

[0020] 1) Core prefabrication

[0021] paraffin powder, cement, expansion agent, silica fume, and sodium lauryl sulfate are mixed in the proportions, and water is added at a water-to-cement volume ratio of 0.3-0.35:1, stirring until uniform to obtain a slurry; the slurry is formed into pellets with a diameter of 1-3 mm using a pressure forming machine at a pressure of 10-15 MPa, and the pellets are dried at 55-65° C. until the moisture content is ≤5%;

[0022] 2) Cyst wall coating

[0023] Dissolve polyvinyl alcohol in deionized water to form a coating solution with a concentration of 5-10 wt%, then suspend the capsule core particles in a hot air flow of 50-60°C, and spray the coating solution by atomization to form a capsule wall of 10-50 μm to obtain microcapsules;

[0024] 3) Surface modification

[0025] The capsule wall surface is plasma treated under an Ar atmosphere to form a groove array with a width of 100-200 nm. The microcapsules are then immersed in a Tris buffer solution containing 2-4 mg / mL polydopamine. The pH of the Tris buffer solution is 8.5. Ultrasonic treatment is performed at 35-40 kHz for 5-8 minutes to allow the Tris buffer solution to penetrate the grooves. Microwave-assisted cross-linking treatment is performed at 280-320 W for 2-4 minutes. Finally, the microcapsules are washed with deionized water 3-5 times to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power is 45-55 W, and the treatment time is 3-7 minutes.

[0026] Description: Plasma power > 45W ensures groove depth > 50nm, and microwave time < 5min prevents excessive cross-linking that may cause coating embrittlement. Microwave-assisted cross-linking promotes the reaction between the catechol groups of polydopamine and the hydroxyl groups of the polyvinyl alcohol capsule wall to form covalent bonds, improving the coating's adhesion and swelling resistance. Plasma treatment creates nano-scale grooves on the surface of the polyvinyl alcohol capsule wall, into which polydopamine is embedded through capillary action, forming a mechanical interlocking structure and improving the coating's peeling resistance.

[0027] The embedded nanogrooves in the polydopamine capsule wall can resist the friction of soil particles, delay one-time rupture, and achieve gradient release of the repair agent; when cracks or pollution concentrations in the soil fluctuate, the undamaged microcapsules can release the repair agent a second time to maintain the repair effect; the acid and alkali resistance of the polydopamine coating adapts to complex soil environments, avoiding premature inactivation of the repair agent, and the self-repair mechanism can respond to changes in soil mechanical stress (such as dry-wet cycles, freeze-thaw effects), ensuring long-term repair capabilities.

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

[0029] Description: CaO initiates the initial expansion, MgO provides medium- and long-term volume compensation, and C3A enhances crack resistance; it adapts to complex soil pH environments; high-purity silica fume can improve the chemical stability of microcapsules and reduce side reactions with capsule core repair agents such as cement and paraffin.

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

[0031] Note: The above temperature can match the thermal sensitivity of the material to avoid denaturation of polydopamine. The above hot air flow rate can ensure uniform suspension of particles and optimize the coating effect. The relative humidity is ≤10% to prevent premature solidification or agglomeration of the coating solution.

[0032] Furthermore, the parameters of atomization spraying are: atomization pressure: 1.0-1.5 MPa, spray rate: 2-5 mL / min, spray gun distance: 15-20 cm, nozzle aperture 0.3-0.5 mm;

[0033] Note: The higher the pressure, the finer the droplets. A too fast spray speed can easily lead to uneven coating. A reasonable spray gun distance can optimize droplet distribution and drying efficiency.

[0034] Furthermore, in S4, the method of microbial remediation treatment is: inoculating white rot fungi into a culture medium, pre-culturing at 28-30°C for 5-7 days to obtain a fungal suspension, mixing the cooled soil with the fungal suspension at a volume ratio of 1:50-55, and adding 2-4wt% lignocellulose as a fungal nutrient source, controlling the soil moisture content at 25-35%, piling thickness ≤30cm, culturing in the dark for 14-15 days, and turning and ventilating the pile every 40-48 hours; then adding calcium dihydrogen phosphate accounting for 4-6wt% of the total amount of the cooled soil, and simultaneously spraying a citric acid-sodium citrate buffer solution with a total concentration of 0.1-0.3 mol / L at a pH of 6.5-7.0, mixing at a speed of 20-30r / min for 30-50min, and then covering with an impermeable membrane and curing at 25-30°C for 7-10 days;

[0035] Description: The white rot fungus is YK-624 (a commercially available product), and 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 HAc-NaAc buffer solution with a pH of 7. Its laccase can further degrade residual PAHs, and the added calcium dihydrogen phosphate can promote the precipitation of heavy metal phosphates, solidify heavy metals, and optimize the soil remediation effect. Turning and aeration can increase the soil pore oxygen content, enhance the activity of aerobic microorganisms, and improve the PAH mineralization rate. The anti-seepage membrane can prevent excessive evaporation of water, minimize moisture content fluctuations, and reduce the difficulty of desorption.

[0036] The beneficial effects of the present invention are:

[0037] (1) The present invention adopts specific remediation treatment methods for the soil in lightly polluted areas and heavily polluted areas respectively. For lightly polluted areas, biochar absorbers are used to achieve low-temperature and high-efficiency desorption of PAHs, avoiding high-temperature damage to soil organic matter; for heavily polluted areas, layered treatment is performed: surface activation of MnO2 catalytic oxidation, deep triggering of persulfate pyrolysis to produce SO4 - Free radicals, achieving deep mineralization of PAHs; MnO2 / magnetite loaded between graphene layers forms a dielectric-magnetic double loss network, improving the efficiency of microwave energy conversion; the three-dimensional pore structure enriches PAHs molecules, increasing the probability of their contact with active free radicals and optimizing their repair effect.

[0038] (2) The self-repairing microcapsules doped with sodium lauryl sulfate prepared by the present invention in a specific manner utilize the gradual release of sodium lauryl sulfate coated in the microcapsules as the temperature rises, thereby enhancing the desorption efficiency of PAHs from soil particles and significantly improving the desorption rate; the controlled release of persulfate can avoid the instantaneous consumption of oxidants and maintain the long-term effectiveness of repair, and polydopamine can resist the friction of soil particles through the nano-grooves embedded in the capsule wall, delaying one-time rupture and realizing the gradient release of the repair agent; when cracks or pollution concentrations in the soil fluctuate, the undamaged microcapsules can release the repair agent for a second time to maintain the repair effect; and the acid and alkali resistance of the polydopamine coating adapts to complex soil environments, making the repair effect more stable.

[0039] (3) The present invention has achieved the following breakthroughs in enhancing the microwave remediation of polycyclic aromatic hydrocarbons contaminated soil with manganese dioxide by embedding the second absorber in the graphene layer: MnO2 loaded between the graphene layers forms a three-dimensional conductive network with magnetite. Under the synergistic effect of graphene increasing dielectric loss and Fe3O4 increasing magnetic loss, the microwave energy conversion efficiency is increased by more than 2 times compared with that of a single material; and the three-dimensional pore structure with a graphene interlayer spacing of ≤1.5nm can preferentially adsorb PAHs molecules and enrich them near the MnO2 active site through π-π interaction, thereby increasing the contact probability, solving the bottleneck problems of instantaneous oxidant consumption and uneven heat energy distribution in traditional microwave remediation, and providing an efficient solution for the control of complex PAHs pollution. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with specific implementation methods to better demonstrate the advantages of the present invention.

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

[0042] S1. Soil zoning: The soil 10m away from the plant is considered as the heavily polluted area; the soil 100m away from the plant is considered as the lightly polluted area;

[0043] S2. Soil pretreatment: 75 g of soil from a heavily polluted area and 75 g of soil from a lightly polluted area were taken, air-dried, passed through a 35-mesh sieve, and dried for 3 days. The soil was then placed in a crucible, water was added to control the soil moisture content to 9%, and microwaved at a microwave power of 850 W for 13 min.

[0044] S3. Strengthening agent preparation: The strengthening agent includes a first absorber and a second absorber; the first absorber is a biochar absorber; the second absorber includes, by weight, 12 parts of manganese dioxide, 2 parts of magnetite, 6 parts of persulfate, and 10 parts of self-repairing microcapsules with a particle size of 2 mm and doped with sodium lauryl sulfate;

[0045] S4. Remediation of contaminated soil:

[0046] For lightly polluted soil: add biochar absorber to the lightly polluted soil at a ratio of 10wt% and mix evenly. Then, microwave treatment is performed at a microwave power of 800W for 9 minutes. After treatment, the soil is cooled to obtain the repaired soil.

[0047] For heavily polluted soil: embed the second absorber into the graphene layer, then evenly mix the second absorber with the heavily polluted soil at a ratio of 6wt% and let it stand for 22 hours; for the 0-20mm surface heavily polluted soil: microwave irradiation at a power of 3kW for 18 minutes, heating to 135°C, holding for 35 minutes, and then cooling to 40°C for microbial remediation; for the 20-50mm deep heavily polluted soil: microwave irradiation at a power of 5kW for 27 minutes, heating to 190°C, holding for 25 minutes, and then cooling to 40°C for microbial remediation;

[0048] The second absorber is embedded in the graphene layer by mixing the second absorber with a graphene oxide suspension at a solid-liquid ratio of 1 g:11 mL, ultrasonically dispersing the mixture at 28° C. and 350 W for 35 minutes to form a homogeneous slurry, then subjecting the mixture to microwave radiation at 800 W for 7 minutes, and freeze-drying the mixture to obtain a composite absorber material. The composite material has a MnO2 loading rate of 15% and a microcapsule encapsulation integrity rate of 90%. The freeze-drying method comprises pre-freezing the mixture at -48° C. for 21 hours, then heating the mixture to -35° C. at a rate of 4° C. / hour, and continuously drying the mixture at a vacuum of 10 Pa for 42 hours until the moisture content reaches 2%.

[0049] The self-healing microcapsules doped with sodium lauryl sulfate include a core repair agent, a capsule wall coated on the outer layer of the core repair agent, and polydopamine with an average molecular weight of 10,000 g / mole arranged on the outer surface of the capsule wall. The core repair agent includes paraffin powder, sodium lauryl sulfate, cement, an expander, and silica fume in a mass ratio of 3:1:5:1:1. The capsule wall material is polyvinyl alcohol. The expander includes: 40% calcium oxide, 30% magnesium oxide, and the balance tricalcium aluminate. The purity of the silica fume is 95%.

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

[0051] 1) Core prefabrication

[0052] Paraffin powder, cement, expansion agent, silica fume, and sodium lauryl sulfate were mixed in proportion, and water was added at a water-to-cement volume ratio of 0.33:1, and stirred until uniform to obtain a slurry; the slurry was formed into pellets with a diameter of 2 mm using a pressure forming machine at a pressure of 13 MPa, and dried at 60°C to a moisture content of 5%;

[0053] 2) Cyst wall coating

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

[0055] 3) Surface modification

[0056] The surface of the capsule wall was plasma treated in an Ar atmosphere to form a groove array with a width of 150 nm. The microcapsules were then immersed in Tris buffer containing 3 mg / mL polydopamine (pH = 8.5). Ultrasonic treatment was performed at 38 kHz for 7 minutes to allow the Tris buffer to penetrate the grooves. Microwave-assisted cross-linking treatment was performed at 300 W for 3 minutes, and the microcapsules were finally 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 minutes.

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

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

[0059] Example 4: Different from Example 1, in S3, the second absorber comprises, by weight, 8 parts of manganese dioxide, 1 part of magnetite, 5 parts of persulfate, and 9 parts of self-healing microcapsules doped with sodium lauryl sulfate and having a particle size of 1 mm.

[0060] Example 5: Different from Example 1, in S3, the second absorber comprises, by weight, 15 parts of manganese dioxide, 3 parts of magnetite, 7 parts of persulfate, and 11 parts of self-healing microcapsules doped with sodium lauryl sulfate and having a particle size of 3 mm.

[0061] Example 6: Different from Example 1, in S4, for lightly polluted soil: a biochar absorber was added to the lightly polluted soil at a ratio of 1 wt % and mixed evenly, and then microwave treatment was performed at a microwave power of 750 W for 8 minutes. After treatment, the soil was cooled to obtain the repaired soil;

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

[0063] Example 7: Different from Example 1, in S4, for lightly polluted soil: a biochar absorber was added to the lightly polluted soil at a ratio of 20 wt % and mixed evenly, and then microwave treatment was performed at a microwave power of 850 W for 10 min. After treatment, the soil was cooled to obtain the repaired soil;

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

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

[0066] Example 9: Different from Example 1, the method of embedding the second absorber into the graphene layer is as follows: the second absorber and the graphene oxide suspension are mixed at a solid-liquid ratio of 1 g:12 mL, ultrasonically dispersed at 30°C and 400 W for 40 minutes to form a homogeneous slurry, and then microwaved at a power of 850 W for 8 minutes, and freeze-dried to obtain a composite absorbing material.

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

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

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

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

[0071] Example 14: Different from Example 1, the expansion agent comprises, by mass percentage, 35% calcium oxide, 25% magnesium oxide and the balance tricalcium aluminate, and the purity of silica fume is 97%.

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

[0073] Example 16: Different from Example 1, paraffin powder, cement, expansion agent, silica fume, and sodium lauryl sulfate are mixed in proportion, and water is added at a water-to-gel volume ratio of 0.3:1 and stirred until uniform to obtain a slurry; the slurry is formed into particles with a diameter of 1 mm using a pressure molding machine with a pressure of 10 MPa, and dried at 55°C to a moisture content of 5%.

[0074] Example 17: Different from Example 1, paraffin powder, cement, expansion agent, silica fume, and sodium lauryl sulfate are mixed in proportion, and water is added at a water-to-gel volume ratio of 0.35:1 and stirred until uniform to obtain a slurry; the slurry is formed into particles with a diameter of 3 mm using a pressure molding machine with a pressure of 15 MPa, and dried at 65°C to a moisture content of 5%.

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

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

[0077] Example 20: Different from Example 1, the surface of the capsule wall is plasma treated under Ar atmosphere to form a groove array with a width of 100 nm, and then the microcapsules are immersed in Tris buffer containing 2 mg / mL polydopamine, the pH of the Tris buffer is 8.5, and ultrasonic-assisted treatment is performed at 35 kHz for 5 minutes to allow the Tris buffer to penetrate into the grooves. Microwave-assisted cross-linking treatment is performed at 280 W for 2 minutes, and finally, the microcapsules are washed with deionized water three times to obtain self-healing microcapsules doped with sodium dodecyl sulfate; the plasma treatment power is 45 W, and the treatment time is 3 minutes.

[0078] Example 21: Different from Example 1, the surface of the capsule wall is plasma treated under Ar atmosphere to form a groove array with a width of 200 nm, and then the microcapsules are immersed in Tris buffer containing 4 mg / mL polydopamine, the pH of the Tris buffer is 8.5, and ultrasonic-assisted treatment is performed at 40 kHz for 8 minutes to allow the Tris buffer to penetrate into the grooves. Microwave-assisted cross-linking treatment is performed at 320 W for 4 minutes, and finally, the microcapsules are washed with deionized water 5 times to obtain self-healing microcapsules doped with sodium dodecyl sulfate; the plasma treatment power is 55 W, and the treatment time is 7 minutes.

[0079] Example 22: Different from Example 1, in S4, the method of microbial remediation treatment is: inoculating white rot fungi into the culture medium, pre-culturing at 29°C for 6 days to obtain a fungal suspension, mixing the cooled soil with the fungal suspension at a volume ratio of 1:53, adding 3wt% lignocellulose, controlling the soil moisture content at 30%, piling thickness of 30cm, culturing in the dark for 14 days, turning and ventilating the pile every 44 hours; then adding calcium dihydrogen phosphate accounting for 5wt% of the total amount of the cooled soil, and simultaneously spraying a citric acid-sodium citrate buffer solution with a total concentration of 0.2mol / L at pH=6.8, mixing at a speed of 25r / min for 40min, and then covering with an impermeable membrane and curing at 27°C for 8 days.

[0080] Example 23: Different from Example 22, in the method of microbial remediation treatment, 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 2 wt% lignocellulose is added. The soil moisture content is controlled at 25%, the stacking thickness is 25 cm, and the culture is carried out in the dark for 14 days, during which the pile is turned and ventilated every 40 hours.

[0081] Example 24: Different from Example 22, in the method of microbial remediation treatment, 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 and the fungal suspension are mixed at a volume ratio of 1:55, and 4wt% lignocellulose is added. The soil moisture content is controlled at 35%, the stacking thickness is 30 cm, and the culture is carried out in the dark for 15 days, during which the pile is turned and ventilated every 48 hours.

[0082] Example 25: Different from Example 22, in the microbial remediation treatment method, calcium dihydrogen phosphate accounting for 4 wt% of the total amount of the cooled soil is added, and a citric acid-sodium citrate buffer solution with a total concentration of 0.1 mol / L and a pH of 6.5 is sprayed simultaneously. The mixture is mixed at a speed of 20 r / min for 30 minutes, and then covered with an impermeable membrane and cured at 25°C for 7 days.

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

[0084] Experimental Example: The actual contaminated soil is yellow-brown soil. Pollutant types and concentrations are shown in Table 1. Soil 0-10 m from the plant site was designated as heavily contaminated, with a total PAH content of 206.63 mg / kg. Soil 100-110 m from the plant site was designated as lightly contaminated, with a total PAH content of 96.8 mg / kg. Polycyclic aromatic hydrocarbons (PAHs) pollutants in this plant area are primarily 3- and 4-ring polycyclic aromatic hydrocarbons. Fluorene and pyrene concentrations in the lightly contaminated soil are similar to those in the heavily contaminated soil, and benzo[g,h,i]perylene is higher in the lightly contaminated soil than in the heavily contaminated soil, indicating the ability of these three pollutants to migrate over long distances.

[0085] Table 1 PAHs content in the soil of an aromatics plant

[0086]

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

[0088] The determination method of PAHs in soil is as follows:

[0089] HPLC / UV assay 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. An acetonitrile-water gradient elution method was used: 0–27.00 min: 65% acetonitrile, 35% water; 27.00–45.00 min: 100% acetonitrile; 45.00–51.00 min: 100% acetonitrile; 51.00–56.00 min: 65% acetonitrile, 35% water; 56.00–60.00 min: 65% acetonitrile, 35% water.

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

[0091] At the same time, a comparative example 1 was set up. The difference between comparative example 1 and embodiment 1 was that the soil was not subjected to microwave treatment.

[0092] Table 2 Effects of Examples 1-3 and Comparative Example 1 on PAHs degradation rates in contaminated soil

[0093]

[0094] Conclusion: Comparison of Examples 1 to 3 with Comparative Example 1 shows that the lack of microwave pretreatment of the soil in Comparative Example 1 resulted in a decrease in the PAHs degradation rate of the soil in the contaminated area. However, the degradation fluctuations of Examples 1 to 3 for the soil in the lightly contaminated area at 30 days and 60 days compared with the first day were ≤5%, and the degradation fluctuations for the soil in the heavily contaminated area at 60 days and 90 days compared with the first day were also ≤9%. This is because microwave pretreatment can activate the heat generation of the absorber, causing it to heat up to 50-60°C, promote the metabolic activity of functional bacteria (such as Pseudomonas), shorten the PAHs degradation cycle, and improve the degradation rate.

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

[0096] Comparative Example 2 and Comparative Example 3 were set at the same time, and the results are shown in Table 3.

[0097] Comparative Example 2: Different from Example 1, the second absorber is not embedded in the graphene layer, and the treatment is performed directly.

[0098] Comparative Example 3: Different from Example 1, the freeze-drying method is: directly drying at -48°C to a water content of 2%.

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

[0100]

[0101] Conclusion: Comparison of Examples 1, 6-9 with Comparative Example 2 shows that direct treatment without embedding the second absorber in the graphene layer in Comparative Example 2 has a significant impact on the PAHs degradation rate of the contaminated soil, as well as the degradation fluctuations over 30 and 60 days in the lightly polluted area and 60 and 90 days in the heavily polluted area. This is mainly because when the second absorber is directly added, manganese dioxide and magnetite are easily agglomerated due to the lack of the fixation effect of graphene, resulting in reduced microwave absorption efficiency and a reduced effective contact area for persulfate (such as potassium persulfate) to release free radicals. This results in loss of dispersion and activity. Microcapsules not embedded in the graphene layer may rupture prematurely under high-temperature microwaves (especially during deep treatment at 190°C), releasing sodium dodecyl sulfate prematurely. Excessive local concentrations may inhibit subsequent oxidation reactions, posing a risk of failure for the self-healing microcapsules. Furthermore, when not embedded in graphene, the absorber is susceptible to adsorption by soil organic matter or water migration, leading to uneven distribution of the oxidant (persulfate). After rapid initial degradation, the active components are depleted, followed by rebound or degradation stagnation in the later stages, increasing the degradation fluctuation of soil in heavily polluted areas to 10-15%.

[0102] By comparing Example 1, Example 10-Example 11 and Comparative Example 3, it can be concluded that the freeze-drying in Comparative Example 3 is directly dried at -48°C to a moisture content of 2%. It has a significant effect on the PAHs degradation rate of the soil in the contaminated area, as well as the degradation fluctuations in the lightly polluted area for 30 and 60 days and the degradation fluctuations in the heavily polluted area for 90 days. This is mainly because the staged freeze-drying forms a uniform porous structure by controlling the heating rate, and the specific surface area is increased by about 35-40%, which helps to enhance the contact activity between the absorber (manganese dioxide, magnetite) and the pollutant; direct freeze-drying causes uneven pore distribution and limited specific surface area due to rapid freezing; direct drying causes the absorber to agglomerate, reduces microwave absorption efficiency, reduces free radical generation, and insufficiency of the PAHs oxidation reaction; and direct drying causes the microcapsules to rupture prematurely, SDS is released rapidly in the early stage, the activity is exhausted in the later stage, the absorber is inactivated, and high-ring PAHs are released secondary, thereby improving the degradation fluctuation of contaminated soil in the lightly polluted area and the heavily polluted area; taking all factors into consideration, the solution of Example 1 of the present application is the best.

[0103] 3. To investigate the effects of self-repairing microcapsules doped with sodium lauryl sulfate and their preparation methods on the degradation rate of PAHs in contaminated soil

[0104] At the same time, comparative examples 4, 5 and 6 were set up, and the results are shown in Table 4.

[0105] Comparative Example 4: Different from Example 1, the second wave absorbing agent does not contain self-repairing microcapsules doped with sodium lauryl sulfate.

[0106] Comparative Example 5: Different from Example 1, polydopamine is not arranged on the surface of the self-repairing microcapsules doped with sodium lauryl sulfate.

[0107] Comparative Example 6: Different from Example 1, polydopamine was directly coated on the surface of the capsule wall.

[0108] Table 4 Effects of Example 1, Example 4-Example 5, Example 12-Example 21 and Comparative Example 4-Comparative Example 6 on the PAHs degradation rate of the contaminated area soil

[0109]

[0110] Conclusion: From the comparison of Examples 1, 4-5, and Comparative Example 4, it can be seen that the self-healing microcapsules without sodium dodecyl sulfate in the second absorber have a significant impact on the PAHs degradation rate in the contaminated soil, as well as the degradation fluctuations in the lightly polluted area over 30 and 60 days, and the degradation fluctuations in the heavily polluted area over 60 and 90 days. This is mainly because after the microcapsules are removed, sodium dodecyl sulfate (SDS) cannot be released gradually with microwave treatment, resulting in a decrease in the persulfate activation efficiency in the soil, a decrease in the initial degradation rate, and an increase in the degradation fluctuation rate.

[0111] From the comparison of Example 1, Example 12 to Example 21 and Comparative Example 5 and Comparative Example 6, it can be seen that the self-repairing microcapsules doped with sodium lauryl sulfate do not arrange polydopamine on the surface or directly coat polydopamine have a significant effect on the PAHs degradation rate of the soil in the contaminated area, as well as the degradation fluctuations in the lightly polluted area for 30 and 60 days, and the degradation fluctuations in the heavily polluted area for 60 and 90 days. This is mainly because the adhesion of polydopamine optimizes the loading stability of MnO2 on the microcapsule surface, thereby increasing the MnO2 loading rate by ≥30%, and polydopamine undergoes structural collapse under a microwave thermal field (>80°C), which can control the staged release of the repair agent, realize the sustainable release of the second absorber, and optimize the PAHs degradation rate and the degradation fluctuation rate over time;

[0112] However, in Comparative Example 6, the directly coated polydopamine layer lacks groove anchoring, so the SDS release rate increases by 2-3 times, resulting in excessive consumption of the initial activation of the oxidant (persulfate), a decrease in the PAHs degradation rate, and a decrease in the mechanical strength of the polydopamine layer that has not been reinforced by the grooves under microwave radiation. The rupture rate of the microcapsules increases in deep soil treatment, and the risk of secondary release of high-ring PAHs (such as benzo[a]pyrene) is significantly increased; direct coating leads to local enrichment of SDS in the soil, the initial oxidation reaction is intense but the later activity is insufficient, and the residual concentration of PAHs rebounds in the later period. Taking all factors into consideration, Example 1 is 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 Example 1, Example 22-Example 26 on PAHs degradation rate in contaminated soil

[0115]

[0116] Conclusion: From the comparison of Example 1 and Example 22-Example 26, it can be seen that the post-treatment of Example 22-Example 26 can significantly improve the PAHs degradation rate of the soil in the contaminated area, as well as the degradation fluctuations of 30 and 60 days in the lightly polluted area and 60 and 90 days in the heavily polluted area. When Example 1 is not inoculated with white rot fungi, the enzyme system (such as lignin peroxidase) cannot continuously degrade the insoluble PAHs, and the residual pollutants are re-adsorbed; when calcium dihydrogen phosphate is missing, the free Fe in the soil 2+ The content is reduced, the activation of persulfate is hindered, and the degradation rate of benzo[a]pyrene is reduced; the failure to add citric acid buffer will cause the soil pH to rise to above 8.5, nanomanganese dioxide (MnO2) will agglomerate and become inactivated, and the oxidation efficiency of high-ring PAHs will decrease; the laccase of white rot fungi can continue to degrade residual PAHs, and the added calcium dihydrogen phosphate can promote the precipitation of heavy metal phosphates, solidify heavy metals, and optimize the soil remediation effect; white rot fungi and persulfate can synergistically decompose high-ring PAHs. When post-treatment is missing, the half-life of benzo[a]pyrene in deep soil is extended, resulting in a decrease in the degradation ability of PAHs; considering all factors, Example 22 is selected as the optimal solution.

Claims

1. A method for enhancing microwave remediation of polycyclic aromatic hydrocarbons contaminated soil, characterized in that: The following steps are involved: S1. Soil zoning: The soil within 0-10m from the plant is considered as the heavily polluted area; the soil within 100-110m from the plant is considered as the lightly polluted area; S2. Soil pretreatment: 50-100 g of soil from a heavily polluted area and 50-100 g of soil from a lightly polluted area were taken, air-dried, passed through a 30-40 mesh sieve, and dried for 2-4 days. The soil was then placed in a crucible, water was added to control the soil moisture content to 8-10%, and microwaved at a microwave power of 800-900 W for 10-15 min. S3. Strengthening agent preparation: The strengthening agent includes a first absorber and a second absorber; the first absorber is a biochar absorber; the second absorber includes, by weight, 8-15 parts of manganese dioxide, 1-3 parts of magnetite, 5-7 parts of persulfate, and 9-11 parts of self-repairing microcapsules with a particle size of 1-3 mm and doped with sodium lauryl sulfate; S4. Remediation of contaminated soil: For lightly polluted soil: add the biochar absorber to the lightly polluted soil at a ratio of 1-20 wt% and mix evenly, then microwave treat the soil at a microwave power of 750-850 W for 8-10 minutes, and cool the soil after treatment to obtain the repaired soil; For heavily polluted soil: embed a second absorber into the graphene layer, then evenly mix the second absorber with the heavily polluted soil at a ratio of 5-7wt%, and let it stand for 20-24 hours. For the 0-20mm surface layer of heavily polluted soil: microwave irradiate at a power of 2.5-3.5kW for 15-20 minutes, heat to 120-150°C, hold for 30-40 minutes, and then cool to 35-45°C for microbial remediation. For soil in heavily polluted areas at a depth of 20-50mm: microwave radiation at a power of 4.5-5.5kW for 25-30 minutes, heating to 180-200℃ and keeping warm for 20-30 minutes, then cooling to 35-45℃ for microbial remediation treatment.

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

3. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 2, characterized in that: The freeze-drying method comprises: pre-freezing at -50 to -45°C for 18-24 hours, then heating to -40 to -30°C at a rate of 3-5°C / h, and continuously drying for 36-48 hours under a vacuum degree of ≤10Pa until the moisture content is ≤2%.

4. The method for enhancing microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 1, characterized in that: The self-repairing microcapsules doped with sodium lauryl sulfate include a core repair agent, a capsule wall coated on the outer layer of the core repair agent, and polydopamine with an average molecular weight of 500-10,000,000 g / mole arranged on the outer surface of the capsule wall; The capsule core repair agent comprises paraffin powder, sodium lauryl sulfate, cement, 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 capsule wall material is polyvinyl alcohol.

5. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 4, characterized in that: The preparation method of the self-repairing microcapsules doped with sodium lauryl sulfate is as follows: 1) Core prefabrication paraffin powder, cement, expansion agent, silica fume, and sodium lauryl sulfate are mixed in the proportions, and water is added at a water-to-cement volume ratio of 0.3-0.35:1, stirring until uniform to obtain a slurry; the slurry is formed into pellets with a diameter of 1-3 mm using a pressure forming machine at a pressure of 10-15 MPa, and the pellets are dried at 55-65° C. until the moisture content is ≤5%; 2) Cyst wall coating Dissolve polyvinyl alcohol in deionized water to form a coating solution with a concentration of 5-10 wt%, then suspend the capsule core particles in a hot air flow of 50-60°C, and spray the coating solution by atomization to form a capsule wall of 10-50 μm to obtain microcapsules; 3) Surface modification The capsule wall surface is plasma treated under an Ar atmosphere to form a groove array with a width of 100-200 nm. The microcapsules are then immersed in a Tris buffer solution containing 2-4 mg / mL polydopamine. The pH of the Tris buffer solution is 8.

5. Ultrasonic treatment is performed at 35-40 kHz for 5-8 minutes to allow the Tris buffer solution to penetrate the grooves. Microwave-assisted cross-linking treatment is performed at 280-320 W for 2-4 minutes. Finally, the microcapsules are washed with deionized water 3-5 times to obtain self-healing microcapsules doped with sodium dodecyl sulfate. The plasma treatment power is 45-55 W, and the treatment time is 3-7 minutes.

6. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 5, characterized in that: The expansion agent comprises, by mass percentage, 35-45% of calcium oxide, 25-35% of magnesium oxide and the balance of tricalcium aluminate. The purity of the silica fume is ≥95%.

7. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 5, characterized in that: The hot air flow rate is 30-50m 3 / h, relative humidity ≤ 10%, temperature 50-60℃.

8. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 5, characterized in that: The parameters of atomization spraying are: atomization pressure: 1.0-1.5MPa, spray speed: 2-5mL / min, spray gun distance: 15-20cm, nozzle aperture 0.3-0.5mm.

9. The method for enhanced microwave remediation of polycyclic aromatic hydrocarbons contaminated soil according to claim 5, characterized in that: In S4, the method for microbial remediation treatment is as follows: inoculating white rot fungi into a culture medium, pre-culturing at 28-30°C for 5-7 days to obtain a fungal suspension, mixing the cooled soil with the fungal suspension at a volume ratio of 1:50-55, adding 2-4wt% lignocellulose, controlling the soil moisture content at 25-35%, piling thickness ≤30cm, culturing in the dark for 14-15 days, turning and ventilating the pile every 40-48h; then adding calcium dihydrogen phosphate accounting for 4-6wt% of the total amount of the cooled soil, and simultaneously spraying a citric acid-sodium citrate buffer solution with a total concentration of 0.1-0.3mol / L at a pH of 6.5-7.0, mixing at a speed of 20-30r / min for 30-50min, then covering with an impermeable membrane, and curing at 25-30°C for 7-10 days.

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