Method for repairing polycyclic aromatic hydrocarbon contaminated soil

Abstract

The invention relates to a method for repairing polycyclic aromatic hydrocarbon contaminated soil, which comprises the following specific steps: S1, eluting the polycyclic aromatic hydrocarbon contaminated soil by using a surfactant to obtain eluted soil; s2, modifying the biochar by adopting a modification solution to obtain modified biochar; and S3, the modified charcoal obtained in the step S2, MoS2 and monopersulfate are mixed and put into the eluted soil obtained in the step S1, and remediation of the polycyclic aromatic hydrocarbon contaminated soil is completed. Compared with the prior art, when the surface active agent, the biochar and the MoS2 technology are comprehensively applied to remediation of the polycyclic aromatic hydrocarbon contaminated soil, the surface active agent is firstly used for enhancing the solubility and the bioavailability of the PAHs; then, the modified biochar is combined with a MoS2 or PMS system to form a composite remediation system, and the removal efficiency and the remediation effect of polycyclic aromatic hydrocarbons (PAHs) can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a method for remediating soil contaminated by polycyclic aromatic hydrocarbons. Background Art

[0002] According to existing research, surfactants play a significant role in the remediation of polycyclic aromatic hydrocarbons contaminated soil. Non-ionic surfactants such as TX100, Tween80, etc. [1] It has been proven that it can effectively improve the solubility and biodegradation rate of PAHs. The effect of non-ionized surfactant Twcen80 on the absorption of phenanthrene and pyrene by ryegrass was studied in a hydroponic system simulation. The results showed that when the initial concentrations of phenanthrene and pyrene in the culture medium were 1.00 mg·L -1 and 0.12 mg·L -1 0~105.6mg·L -1 Within the range, low concentrations of Twcen80 can promote the absorption of phenanthrene and pyrene by roots and grass leaves. However, current research is mostly limited to the effects of rhizosphere repair of PAHs pollution before and after the application of surfactants, and there is little research on the action process and mechanism of surfactants. The rhizosphere repair technology combined with plant-surfactant will become a new research focus in the field of rhizosphere repair of PAHs contaminated soil. In addition, some specific biosurfactants such as lactic acid glyceride and BS29 bioemulsion also show good effects. [2-5] These surfactants promote the release and biodegradation of PAHs from soil by increasing their water solubility.

[0003] Surfactants can significantly increase the solubility of PAHs, thereby improving their elution efficiency from soil. Studies have shown that different types of surfactants have different elution effects on PAHs. For example, Triton X-100 has the highest weight solubility in removing acetylnaphthalene and fluorescent pyrene. In addition, the elution effect can be further optimized by adjusting factors such as surfactant concentration, elution time and solid-liquid ratio. [9] .

[0004] Surfactants can change the surface charge and absorption potential of soil, thereby affecting the occurrence form or solubility of pollutants. This change helps to improve the desorption capacity of pollutants from soil and promote their bioremediation.

[0005] In the process of removing heavy metals and radionuclides, surfactants also involve dissolution, complexation and ion exchange mechanisms. These mechanisms are also applicable to the removal of PAHs, making pollutants easier to remove by forming stable complexes or ion exchange complexes.

[0006] Surfactants not only have good remediation effects when used alone, but can also be combined with other remediation technologies such as chemical, biological or physical technologies to enhance the overall remediation efficiency. For example, in the soil remediation of hydrophobic organic contaminants (HOCs), surfactants are often used to improve the treatment efficiency of other remediation technologies.

[11] .

[0007] Although traditional surfactants show high elution rates during the remediation process, they may cause secondary pollution to the soil. Therefore, researchers are also exploring new environmentally friendly surfactants, such as the gemini anionic surfactant AGS, and non-ionic surfactants Tween-80, Triton X-100, etc., in order to find a remediation technology that is both environmentally friendly and economical.

[0008] Biochar is a highly efficient adsorption material, and its adsorption capacity for pollutants can be enhanced by introducing different functional groups. For example, ammonia activation can increase the amino groups on the surface of biochar, while plasma activation helps to increase the oxygen-containing functional groups. [6] In addition, metal impregnation technology has also been used to increase the specific surface area and catalytic active sites of biochar, thereby enhancing its catalytic performance.

[0009] Acid-base modification is the process of treating biochar with acid or alkaline solutions to change its specific surface area and pore volume and introduce surface functional groups to improve its adsorption performance. For example, the modification of wood chip-based biochar with ammonia can introduce amino functional groups on the surface, which have a strong affinity with certain pollutants (such as copper ions).

[0010] Physical modification methods mainly include high-temperature calcination, etc. Through high-temperature calcination (heating at 800℃~900℃ for 1~2 hours), organic matter and other impurities in the pores of biochar can be removed, its pore structure can be changed, and the specific surface area can be increased, thereby enhancing its adsorption capacity.

[0011] Chemical modification methods include using different chemical reagents to treat biochar. For example, using acidic and alkaline chemical reagents such as HNO3, H2SO4, H3PO4, Na2CO3, NH3·H2O, NaOH, Ca(OH)2 to modify biochar, and by pretreatment, mixing, impregnation and other methods to regulate the surface acidity and alkalinity of biochar, its surface properties and adsorption performance can be significantly changed.

[0012] The biological modification method is to use microorganisms or other biological materials to treat biochar. For example, by fixing Yarrowia lipolytica Tzyx3 on biochar to form a biochar agent, the removal efficiency of polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, and pyrene in water can be significantly improved.

[0013] Preparation of composite materials is also an effective modification method. For example, loading P-doped g-C3N4 onto biochar can significantly improve the photocatalytic degradation efficiency of naphthalene, with a removal rate of 76.41%, a first-order kinetic reaction rate constant of 0.0084 min^-1, which is 3.1 times that of pure g-C3N4.

[0014] Iron-loaded biochar has also been used to enhance the removal mechanism of PAHs in constructed wetlands. This modification method enhances the removal capacity of PAHs by adding iron to biochar.

[0015] These studies showed that the removal efficiency of PAHs by biochar could be significantly improved through different modification methods.

[0016] As a metastable metallic material, MoS2 exhibits excellent catalytic performance in activated monopersulfate (PMS) system. PMS is an effective sulfate radical precursor that can produce highly oxidizing SO4 - Free radicals, used to degrade refractory organic matter. MoS2 can not only activate PMS through thermal activation, acoustic activation, etc., but also further improve its catalytic efficiency through photoactivation.

[0017] As a heterogeneous metal catalyst, MoS2 can effectively activate PMS and produce active oxygen species with strong oxidizing properties, thereby removing refractory organic matter in water. Studies have shown that MoS2 nanosheets can significantly improve the activation efficiency of PMS through the piezoelectric effect. When compressive strain is applied, MoS2 nanosheets can produce hydroxyl radicals (·OH), which are further converted into SO4 - · Free radicals, thereby enhancing the activation effect of PMS ( Figure 3 ).

[0018] In the US / MoS2NFs / PMS system, the combination of ultrasound (US) and MoS2 nanoflowers (NFs) further improves the activation efficiency of PMS. The experimental results show that the degradation efficiency of this combined system is higher than that of the single system, revealing the synergistic effect of US and MoS2 on PMS activation. Density functional theory calculations further clarify the charge distribution in polarized MoS2 nanosheets under different strains and explain the piezoelectric catalytic properties of MoS2 nanosheets and the reaction pathway between PMS and MoS2 active edge supports ( Figure 4 ).

[0019] MoS2 has also demonstrated its superior performance in removing specific pollutants. For example, studies have shown that MoS2 enhances Fe 2+ The activated PMS system can effectively remove sulfamethoxazole (SMX) and reduce hexavalent chromium (Cr(VI)) in the solution. [7]In addition, MoS2 has also been used to activate PMS to remove organic pollutants such as tetracycline (TC).

[0020] MoS2 can also be combined with other materials to form composite materials to improve its catalytic performance. For example, Fe3O4 / MoS2 composites synthesized by hydrothermal method showed excellent ability to degrade 2,4-dichlorophenoxyacetic acid (2,4-D) [8] In addition, the CoFe2O4@MoS2 composite material also demonstrated efficient tetracycline degradation ability.

[0021] MoS2 not only performs well in laboratory studies, but also has potential for application in actual environmental remediation. For example, the piezoelectric activation of persulfate by MoS2 nanoflowers [9] , which can promote the degradation of water-based organic pollutants and provide new ideas for the use of natural mechanical energy in environmental remediation.

[0022] The combination of MoS2 and monopersulfate system has significant advantages in the field of water treatment. It can effectively degrade refractory organic pollutants by catalytically activating PMS to produce strong oxidizing free radicals.

[10] At the same time, the composite application of MoS2 with other materials further enhances its catalytic performance and environmental remediation potential.

[0023] MoS2 as a heterogeneous metal catalyst can effectively activate PMS to remove refractory organic matter in water. 2+ In the / PMS system, the degradation rate of sulfamethoxazole (SMX) can reach 88.5% after 6 minutes of reaction, which is much higher than that of Fe 2+ / PMS or MoS2 / PMS system for SMX degradation at 6 minutes. MoS2 can accelerate the degradation of Fe 2+ The activation of PMS and peroxydisulfate (PDS) generates a large number of reactive oxygen species (ROS), such as OH, SO4 - · and 1O2. Therefore, the introduction of MoS2 effectively promotes the free radicals (·OH, SO4 - ·), the formation of 1O2 and Fe(IV), which improves the efficiency of the PMS activation process.

[0024] Increasing the defect density of active sites, edge sites, and basal planes and regulating the electronic structure and crystal phase are effective strategies to improve the intrinsic catalytic activity and overall catalytic performance of MoS2. Doping multi-metals on iron-based catalysts has been shown to be an effective way to improve the persulfate activation performance. For example, by introducing MoS2 on the surface of FeCo nanoboxes, an efficient persulfate activation catalyst (FeCo@MoS2) was successfully synthesized with better catalytic performance. The layered MoS2 with the strongest piezoelectric activity was synthesized and screened using different methods, and loaded on a porous ceramic support, which can further improve its catalytic performance. MoS2 exhibits excellent catalytic performance in the activated monopersulfate system, especially in combination with Fe. 2+ When used in combination with other metal ions, the degradation efficiency can be significantly improved. Summary of the invention

[0025] The purpose of the present invention is to provide a method for remediating soil contaminated by polycyclic aromatic hydrocarbons. When the present invention comprehensively applies surfactant, biochar and MoS2 technology to the remediation of soil contaminated by polycyclic aromatic hydrocarbons (PHE, PYR, BaP), the surfactant is first used to enhance the solubility and bioavailability of PAHs. Then, the modified biochar is combined with MoS2 or PMS system to form a composite remediation system, which can improve the removal efficiency and remediation effect of polycyclic aromatic hydrocarbons (PAHs).

[0026] The purpose of the present invention can be achieved by the following technical solutions:

[0027] A method for repairing soil contaminated by polycyclic aromatic hydrocarbons, the specific steps are as follows:

[0028] S1. treating the polycyclic aromatic hydrocarbons-contaminated soil by eluting with a surfactant to obtain eluted soil;

[0029] S2, modifying the biochar using a modification solution to obtain modified biochar;

[0030] S3. Mix the modified biochar, MoS2 and monopersulfate obtained in step S2 and add them to the soil after elution treatment obtained in step S1 to complete the remediation of the soil contaminated by polycyclic aromatic hydrocarbons.

[0031] Furthermore, in step S1, the polycyclic aromatic hydrocarbons include PHE, PYR and BaP.

[0032] Furthermore, in step S1, the polycyclic aromatic hydrocarbons contaminated soil is ground and sieved, a surfactant solution is added, and oscillation and centrifugal extraction are performed to obtain the eluted soil.

[0033] Furthermore, in step S1, the surfactant is C12-ED3A3Na, the concentration of the surfactant is 6000 mg / L, and the pH is 11.72.

[0034] Furthermore, in step S1, the elution time is 4 hours.

[0035] Furthermore, in step S2, the biochar preparation method is as follows:

[0036] Weigh an appropriate amount of pine sawdust, dry and sieve it, immerse the sieved sawdust powder in NaOH solution and wash until the pH value is stable; then immerse it in HCl solution, repeat several times and dry it for use; heat it to 400℃ at a heating rate of 5℃ / min and then anaerobic incinerate it at a constant temperature for 2h to obtain biochar.

[0037] Furthermore, in step S2, the solid-liquid ratio of the biochar and the modified solution is 1g:(20-1000mL).

[0038] Furthermore, in step S2, the modified solution includes HNO3, H3PO4, Ca(OH)2 and NH3·H2O.

[0039] In the above further aspect, the modified solution is H3PO4.

[0040] Furthermore, in step S3, the modified biochar, MoS2 and monopersulfate obtained in step S2 are evenly sprinkled on the eluted soil obtained in step S1, and then plant seedlings are transplanted, watered, and field managed. Sowing is repeated 2-5 times to repair the soil contaminated by polycyclic aromatic hydrocarbons in situ.

[0041] Furthermore, in step S3, the amount of modified biochar obtained in step S2 is 4-5 kg / m 2 The dosage of monopersulfate is 4-6 kg / m 2 The mixing depth is 10-20 cm, and the amount of MoS2 added is 2-3 kg / m 2 , the mixing depth is 10 to 20 cm.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. The present invention combines modified biochar with MoS2 or PMS system to form a composite remediation system, verifies the effect of the composite system through experiments, and continuously optimizes parameters according to actual application conditions. For example, the removal efficiency of surfactants, the optimal ratio of biochar and MoS2, and the action time are tested under different concentrations and temperatures.

[0044] 2. The method of using composite surfactants to enhance the biochar-loaded MoS2 or monopersulfate system significantly improves the remediation effect of PAHs-contaminated soil through multi-faceted synergistic effects. This method is not only highly efficient and environmentally friendly, but can also be widely used in the remediation of PAHs-contaminated soils of different types and degrees.

[0045] 3. In the process of studying the adsorption of heavy metals by biochar, the present invention found that carboxyl, hydroxyl, amino and other groups contribute more, so HNO3, H3PO4, Ca(OH)2 and NH3·H2O are selected as acid and alkali modification solutions to regulate the surface functional groups of biochar.

[0046] 4. To optimize the ratio of nonionic surfactants and chelating surfactants in the remediation of PAH-contaminated soil, multiple factors need to be considered, including the type, concentration, elution time, solid-liquid ratio and their compounding effect of surfactants. Nonionic surfactants such as Triton X-100, AEO-9 and Tween80 have shown good effects in treating naphthalene-contaminated soil. Chelating surfactants such as sodium N-lauroylethylenediaminetriacetate (LED3A) and C 12 -ED3A3Na also showed high efficiency in treating soils contaminated by heavy metals and PAHs; the concentration of surfactants had a significant effect on the elution effect. For example, Triton X-100 can effectively remove PAHs at a concentration of 8g / L. At the same time, the nonionic surfactant Brij30 significantly improved the desorption of PAHs at a lower dose, while C12E8 did not enhance PAH removal at any dose; the combination of nonionic and chelating surfactants may produce a synergistic effect

[13] For example, when the chelating surfactant LED3A is used in combination with a nonionic surfactant, it can effectively remove cadmium and pyrene from the soil at the same time; chelating surfactants such as ED3A surfactants are safe for the environment, have a fast biodegradation rate, and are almost non-toxic to mammals and aquatic plants and animals.

[0047] 5. The present invention optimizes the use ratio of nonionic surfactants and chelating surfactants based on the following steps: Preliminary screening: Select nonionic and chelating surfactants with higher elution efficiency. Concentration optimization: Determine the optimal concentration through experiments to achieve the highest elution efficiency. Compounding experiment: Explore the compounding ratio of nonionic and chelating surfactants to find the best combination. Environmental assessment: Ensure that the selected surfactants are safe for the environment and have good biodegradability.

[0048] 6. The preparation method and type of biochar have a significant impact on the removal efficiency of polycyclic aromatic hydrocarbons (PAHs). Depending on the preparation method, the physical and chemical properties of biochar will vary, which will affect its adsorption and degradation capacity for PAHs. Pyrolysis: Biochar prepared by high-temperature pyrolysis usually has larger pores and specific surface area, which helps to improve its adsorption capacity. Hydrothermal carbonization: This method uses high-temperature liquid water as a medium, which can dissolve organic and inorganic matter at the same time, so the prepared biochar may have higher chemical activity and adsorption capacity. Gasification and microwave pyrolysis: These methods can also prepare biochar with different pore structures and surface characteristics, which affects its removal efficiency for PAHs.

[0049] 7. Biochars from different raw material sources differ in pore size, porosity, and specific surface area, and these differences can affect their ability to adsorb and degrade PAHs. For example, rice husk biochar has been shown to have the ability to efficiently degrade PAHs in immobilized bacterial agents. Biochars made from Taxus and Bridal Wreath showed high adsorption efficiency in removing PAHs from urban stormwater runoff, especially under 300°C combustion conditions, where the adsorption efficiency for pyrene can reach 88%. Biochar can not only remove PAHs by physical adsorption, but also by biodegradation through immobilized microbial agents. For example, the bacterial agent formed by biochar-immobilized Yarrowia lipolytica showed significant synergistic effects in removing naphthalene, phenanthrene, and pyrene from water bodies.

[12] .

[0050] 8. In the monopersulfate (PMS) system, cobalt ions (Co2+) have been shown to have the best activation performance. However, the high biological toxicity of cobalt ions may lead to secondary pollution problems, so measures need to be taken to control their toxicity. In order to effectively activate PMS and control toxicity, other transition metal ions can be considered as alternatives. For example, iron ions (Fe2+) and manganese ions (Mn2+) have also been widely studied for the activation of PMS.

[14] , and they are less toxic than cobalt ions. In particular, iron ions and manganese ions have gradually become substitutes for cobalt oxides due to their environmental friendliness, low cost and easy availability. In the process of using transition metal ions to activate PMS, the optimal molar ratio of metal ions to PMS is an important factor in determining the activation effect. For example, the optimal activation molar ratio of PMS and Fe2+ is 1:1, and in the process of adding metal ions, adding the activator one by one can obtain a better degradation effect than adding all of it directly. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 C 12 -Effect of ED3A3Na concentration on phenanthrene removal efficiency;

[0052] Figure 2 The effect of elution time on the removal rate of phenanthrene;

[0053] Figure 3 The mechanism of the activation effect of PMS enhanced by MoS2 nanosheets;

[0054] Figure 4 It is the reaction pathway between PMS and MoS2 active edge carriers;

[0055] Figure 5 The adsorption data of Cr(VI) by biochar before and after acid-base modification and the fitting results of Langmuir and Freundlich isotherm models. DETAILED DESCRIPTION

[0056] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0057] In conjunction with the accompanying drawings, some embodiments of the present invention are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0058] Example 1

[0059] This embodiment provides a method for treating soil contaminated with polycyclic aromatic hydrocarbons with a surfactant, and the specific steps are as follows:

[0060] The polycyclic aromatic hydrocarbons (PHE, PYR, BaP) contaminated soil was ground through a 60-mesh (0.42 mm) sieve, 0.5 g of the contaminated soil was placed in a 50 mL centrifuge tube, and 10 mL of surfactant solution was added. Three replicates were set for each treatment. The centrifuge tube was placed in a constant temperature shaker and horizontally shaken for 24 h (25 ° C, 150 r / min). The centrifuge tube was centrifuged at high speed (3 000r / min, 10min), let it stand, take 2mL of supernatant and use 10mL of extractant (the volume ratio of n-hexane to dichloromethane is 1:1) for ultrasonic extraction for 1h, take 5mL of the lower layer extract to pass through a solid phase extraction column (SPE, the solid phase extraction column is filled with 1g of anhydrous sodium sulfate, silica gel, Florisil and anhydrous sodium sulfate from bottom to top), the SPE column is activated with 5mL of n-hexane, and after purification, the rotary concentration evaporation flask and the SPE column are rinsed 3 times with a mixed solution of n-hexane and dichloromethane in a volume ratio of 9:1, the purified liquid is placed on a rotary evaporator and concentrated again to 2mL, 1mL of acetonitrile is added to concentrate to less than 1mL, the volume is made up to 1mL with acetonitrile, and the liquid is measured on a liquid chromatograph.

[0061] Example 2

[0062] This embodiment provides an optimization method for treating polycyclic aromatic hydrocarbons contaminated soil with a surfactant, and the specific steps are as follows:

[0063] S1. Single factor experiment on the concentration of the new chelating surfactant C12-ED3A3Na

[0064] The soil was treated with a new chelating surfactant C12-ED3A3Na. The elution time was 4 h, the water-soil ratio was 20:1, the temperature was 25°C, the pH of the C12-ED3A3Na solution was 11.72, and the concentrations of C12-ED3A3Na were 0 mg / L, 500 mg / L, 1000 mg / L, 2000 mg / L, 4000 mg / L, 6000 mg / L, and 8000 mg / L, respectively.

[0065] like Figure 1 As shown in the figure, it can be seen that when the concentration of C12-ED3A3Na is less than 1000 mg / L, the removal rate of phenanthrene increases rapidly with the increase of its concentration; 12 When the concentration of -ED3A3Na continued to increase to 2000 mg / L, the removal rate of phenanthrene decreased, and then with the increase of C 12 -ED3A3Na concentration increases, the removal rate of phenanthrene continues to rise. 12 When the concentration of -ED3A3Na was 6000mg / L, the removal rate of phenanthrene reached the highest point, which was 85.44%. 12 -ED3A3Na concentration, the removal rate of phenanthrene decreased again. From the overall trend, the removal rate of phenanthrene decreased with the increase of C 12 -ED3A3Na concentration increases, reaches a peak, and then increases C 12 -ED3A3Na concentration will reduce the removal rate of phenanthrene. This is because C 12 As the concentration of -ED3A3Na increases, the number of micelles in the aqueous phase increases, and its ability to solubilize phenanthrene increases, so the removal rate of phenanthrene increases; however, when C 12 When the concentration of -ED3A3Na increases to a certain extent, the viscosity of the solution increases, and the micelles are easily adsorbed in the soil, resulting in a decrease in the removal rate of phenanthrene.

[0066] S2. Single factor experiment on elution time of new chelating surfactant C12-ED3A3Na

[0067] The soil was treated with a new chelating surfactant C12-ED3A3Na. The concentration of C12-ED3A3Na was 6000 mg / L, the water-soil ratio was 20:1, the temperature was 25°C, the pH of the C12-ED3A3Na solution was 11.72, and the elution times were 20 min, 40 min, 60 min, 240 min, 480 min, and 600 min, respectively.

[0068] Figure 2 It shows that within 240 minutes of elution time, the elution rate of phenanthrene rises rapidly, and at 240 minutes, the elution rate reaches a peak; then, as the elution time is further extended, the removal rate of phenanthrene shows a downward trend. This may be due to the effect of phenanthrene-surfactant-soil. In the early stage of elution, the surfactant desorbs phenanthrene from the soil and solubilizes it in the surfactant micelles at a fast rate, while the rate at which the surfactant micelles adsorb on the soil is relatively slow. Therefore, the removal rate of phenanthrene shows an upward trend; however, in the later stage of elution, many surfactant micelles that solubilize phenanthrene are also adsorbed in the soil, resulting in a decrease in the removal rate of phenanthrene.

[0069] Therefore, when the concentration of C12-ED3A3Na was 6000 mg / L and the elution time was 4 h, the extraction efficiency of PAHs was the highest.

[0070] Example 3

[0071] This embodiment provides a method for preparing biochar, and the specific steps are as follows:

[0072] Pine sawdust was selected as the raw material for preparing biochar. An appropriate amount of pine sawdust was weighed and dried at 105°C. The dried pine sawdust was pretreated to wash away soluble substances and reduce the error of subsequent experiments. According to the solid-liquid ratio of 20 / L, the sawdust powder after passing through a 100-mesh sieve was immersed in a 0.05mol / LNaOH solution, fully stirred for 24h, and then washed with deionized water until the pH value was stable; then immersed in a 0.05mol / L HCI solution, the above experimental operation was repeated, and finally placed in a 60°C oven for drying for standby use. An aluminum box (50mm in diameter and 30mm in height) containing an appropriate amount of dried sawdust was placed in a box-type atmosphere furnace. First, N2 was introduced for 30min to exhaust the oxygen in the pyrolysis furnace, and then heated at a heating rate of 5°C / min, and finally maintained at 400°C for 2h, and then N2 was continued until it naturally cooled to about 100°C. The obtained biochar was collected and stored in a dryer for subsequent experiments. The obtained biochar was named AB400.

[0073] Example 4

[0074] This embodiment provides a method for modifying biochar using different modification solutions, and the specific steps are as follows:

[0075] HNO3 modification: AB400 (biochar) was placed in a 20% HNO3 solution at a solid-liquid ratio of 1 g / L, stirred continuously for 12 h at 25 °C, then filtered, washed with deionized water to about pH = 7, and then placed in a vacuum drying oven at 105 °C for 48 h. The obtained product was recorded as AB400HNO3.

[0076] H3PO4 modification: AB400 was placed in a 2 mol / L H3PO4 solution at a solid-liquid ratio of 1 g / 100 mL, stirred continuously at 25 °C for 8 h, then filtered, washed with deionized water to about pH = 7, and then placed in a vacuum drying oven at 105 °C for 48 h. The obtained product was recorded as AB400H3PO4.

[0077] Ca(OH)2 modification: AB400 was placed in the supernatant of a saturated Ca(OH)2 solution at a solid-liquid ratio of 1 g / 100 mL, soaked at 25°C for 48 hours, then filtered, washed with deionized water to about pH = 7, and then dried in a vacuum drying oven at 105°C for 48 hours. The resulting product was recorded as AB400Ca(OH)2.

[0078] NH3·H2O modification: AB400 biochar was placed in a 12.5% ​​NH3·H2O solution at a solid-liquid ratio of 1 g / 20 mL, immersed at 25 °C for 8 h, then filtered, washed with deionized water to about pH = 7, and then dried in a vacuum drying oven at 105 °C for 48 h. The resulting product was recorded as AB400NH4OH.

[0079] Comparison of the adsorption capacity of biochar for Cr(VI) before and after modification is shown in Figure 5 The isothermal adsorption parameters obtained by fitting are shown in Table 1. It can be seen that the Langmuir fitting correlation coefficients of AB400, AB400HNO3, AB400H3PO4, AB400Ca(OH)2, and AB400NH4OH (0.974, 0.982, 0.966, 0.986, and 0.952) are all better than Freundlich (0.925, 0.961, 0.922, 0.980, and 0.932). This shows that the Langmuir adsorption model is more suitable for the adsorption of Cr(VI) by biochar. Since the surface of biochar is porous and the oxygen-containing functional groups it carries are related to the composite ion radius of width=99, height=17, and dpi=110, this shows that the adsorption process of biochar on Cr(VI) is monolayer adsorption.

[0080] Table 1 Parameter fitting results of isothermal adsorption model of Cr(VI) adsorption by acid-base modified biochar

[0081]

[0082] Depend on Figure 5As shown in Table 1, the adsorption capacity of biochar for Cr(VI) before modification is 58.48 mg / g; after modification, the biochar modified with H3PO4 (AB400H3PO4) has the strongest adsorption capacity for Cr(VI), and the saturated adsorption capacity can reach 101.82 mg / g, which is much higher than other modified biochars; while the adsorption capacity of biochar modified with HNO3, Ca(OH)2 and NH3·H2O for Cr(VI) is reduced.

[0083] Composite surfactants can enhance the adsorption capacity and reactivity of biochar, thereby improving the remediation efficiency. However, when using these chemicals, their concentration and usage must be strictly controlled to avoid the generation of new secondary pollution. When composite surfactants are used to enhance the remediation of PAH-contaminated soils by biochar-loaded MoS2 or monopersulfate systems, the choice of remediation technology, the risk assessment of secondary pollution during the remediation process, and the use specifications of composite surfactants must be comprehensively considered.

[0084] In summary, the method of using composite surfactants to enhance biochar-loaded MoS2 or monopersulfate system to remediate polycyclic aromatic hydrocarbons contaminated soil can significantly improve the bioavailability and remediation efficiency of PAHs by selecting appropriate surfactants and optimizing their use conditions. This method combines the advantages of chemical and biological remediation technologies and provides a new strategy for efficient and environmentally friendly soil remediation.

[0085] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

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Claims

1. A method for remediating soil contaminated by polycyclic aromatic hydrocarbons, characterized in that: The specific steps are as follows: S1. treating the polycyclic aromatic hydrocarbons-contaminated soil by eluting with a surfactant to obtain eluted soil; S2, modifying the biochar using a modification solution to obtain modified biochar; S3. Mix the modified biochar, MoS2 and monopersulfate obtained in step S2 and add them to the soil after elution treatment obtained in step S1 to complete the remediation of the polycyclic aromatic hydrocarbons contaminated soil.

2. A method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S1, the polycyclic aromatic hydrocarbons include PHE, PYR and BaP.

3. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S1, the polycyclic aromatic hydrocarbons contaminated soil is ground and sieved, a surfactant solution is added, and oscillation and centrifugal extraction are performed to obtain the eluted soil.

4. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S1, the surfactant is C12-ED3A3Na, the concentration of the surfactant is 6000 mg / L, and the pH is 11.

72.

5. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S1, the elution time is 4 hours.

6. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S2, the biochar preparation method is as follows: Weigh an appropriate amount of pine sawdust, dry and sieve it, immerse the sieved sawdust powder in NaOH solution and wash until the pH value is stable; then immerse it in HCl solution, repeat several times and dry it for use; heat it to 400℃ at a heating rate of 5℃ / min and then anaerobic incinerate it at a constant temperature for 2h to obtain biochar.

7. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S2, the solid-liquid ratio of the biochar to the modified solution is 1 g:(20-1000 mL).

8. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S2, the modified solution includes HNO3, H3PO4, Ca(OH)2 and NH3·H2O.

9. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S3, the modified biochar, MoS2 and monopersulfate obtained in step S2 are evenly sprinkled on the eluted soil obtained in step S1, and then plant seedlings are transplanted, watered, and field managed. Sowing is repeated 2-5 times to repair the soil contaminated by polycyclic aromatic hydrocarbons in situ.

10. The method for remediating soil contaminated by polycyclic aromatic hydrocarbons according to claim 1, characterized in that: In step S3, the amount of modified biochar obtained in step S2 is 4-5 kg / m 2 The dosage of monopersulfate is 4-6 kg / m 2 The mixing depth is 10-20 cm, and the amount of MoS2 added is 2-3 kg / m 2 , the mixing depth is 10 to 20 cm.

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