Method for combined biocarbons and phytoremediation of polycyclic aromatic hydrocarbon contaminated soil

Abstract

The application discloses a method for remediating polycyclic aromatic hydrocarbon contaminated soil by biomass carbon combined with plant synergy, comprising the following steps: S1, modified biomass carbon preparation: S1-1, cultivating modified biomass carbon preparation; S1-2, putting modified biomass carbon preparation; S2, cultivating soil preparation; S3, cultivating remediation plants; S4, soil combined remediation. The application prepares two different modified biomass carbons and uses them in different situations, so that the two modified biomass carbons are more suitable for each other and can maximize the adsorption effect, the two modified biomass carbons are respectively used in different situations to maximize their respective functions, and the two modified biomass carbons are respectively loaded with Fe and Cu, so that the two modified biomass carbons can produce a synergistic effect, a redox cycle is generated in the soil, and the modified biomass carbon has better activation capacity for PMS compared with single modified biomass carbon.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil pollution treatment, in particular to a method for remediating polycyclic aromatic hydrocarbon (PAHs) contaminated soil by biomass carbon combined with plant. BACKGROUND

[0002] PAHs refer to aromatic hydrocarbons containing two or more benzene rings, which are referred to as PAHs. The source of PAHs is divided into natural source and human source. The natural source mainly comes from the biosynthesis process of land, aquatic plants and microorganisms, in addition, the natural fire of forest and grassland and the eruption of volcanoes and PAHs from fossil fuels, lignin and sediment also exist; the human source is mainly formed by the incomplete combustion or pyrolysis of various mineral fuels, wood, paper and other hydrocarbon-containing compounds under reducing conditions. PAHs have toxicity, genotoxicity, mutagenicity and carcinogenicity, and can cause various harms to the human body, such as damage to the respiratory system, circulatory system and nervous system, and damage to the liver and kidney. It is recognized as a major organic pollutant affecting human health.

[0003] Removing PAHs from the environment is considered the most important method to restore the contaminated environment. Many physical and chemical treatment methods have been tried, including incineration, alkali catalytic dechlorination, ultraviolet oxidation, fixation, solvent extraction, etc., but these methods have the disadvantages of high cost, complexity, difficulty in regulation and control, etc. In addition, these traditional environmental remediation technologies are difficult to completely remove these pollutants in many cases, but only transfer them from one environment to another or form another pollutant. At present, bioremediation and semiconductor photocatalytic degradation technology are better methods for removing PAHs.

[0004] Bioremediation is a remediation technology that uses microorganisms and plants to remove organic pollutants in the environment through cell metabolism or the production of hydrolytic enzymes. Microorganisms can secrete enzymes to connect the benzene rings on PAHs and convert PAHs into alcohol or phenolic substances through hydrogenation and ring-opening processes to repair. Plant remediation mainly absorbs and enriches pollutants through plant roots or promotes the degradation of PAHs through root exudates. Enzymes in plant root exudates not only directly participate in the degradation of PAHs, but also provide a large amount of nutrients for microorganisms to promote the growth of microorganisms, thereby improving the degradation efficiency of PAHs. Bioremediation is widely used in the treatment of PAHs pollution due to its simple operation, low cost and no secondary pollution, but the removal effect of this technology on high-concentration and complex-structure pollutants is very poor, and it is limited by the actual contaminated site. Therefore, bioremediation technology still faces a series of challenges. SUMMARY

[0005] In view of the above problems, the present application provides a method for remediating polycyclic aromatic hydrocarbon (PAHs) contaminated soil by biomass carbon combined with plant.

[0006] The technical scheme of the present application is:

[0007] The method for combined remediation of polycyclic aromatic hydrocarbon contaminated soil by biomass carbon and plants comprises the following steps:

[0008] S1, preparation of modified biomass carbon:

[0009] S1-1, preparation of modified biomass carbon for cultivation: mix modified pine cone powder, metakaolin and FeSO4·7H2O powder according to a mass ratio of 1:2:4-5, dissolve and stir with water, and then obtain first premixed powder after drying; add the first premixed powder to a Na2SiO3 solution and stir to mix, and then obtain first mixed powder after drying; and then obtain modified biomass carbon for cultivation by calcining the first mixed powder at 700-750℃ for 2-3h under a nitrogen atmosphere.

[0010] S1-2, preparation of modified biomass carbon for release: mix modified pine cone powder, metakaolin and CuSO4·5H2O powder according to a mass ratio of 1:0.5:3-4, dissolve and stir with water, and then obtain second premixed powder after drying; add the second premixed powder to a Na2SiO3 solution and stir to mix, and then obtain second mixed powder after drying; and then obtain modified biomass carbon for release by calcining the second mixed powder at 700-750℃ for 2-3h under a nitrogen atmosphere.

[0011] S2, preparation of cultivation soil: place the crushed uncontaminated soil in a culture container, and then mix in the modified biomass carbon for cultivation, wherein the mass ratio of the modified biomass carbon for cultivation to the uncontaminated soil is 1:500-1000, and then obtain cultivation soil.

[0012] S3, cultivation of remediation plants: sprinkle rye seeds into the cultivation soil for cultivation, and then obtain rye seedlings.

[0013] S4, combined remediation of soil: mix the modified biomass carbon for release and persulfate PMS into the polycyclic aromatic hydrocarbon contaminated soil to be treated, transplant the rye seedlings into the polycyclic aromatic hydrocarbon contaminated soil, and then intercrop with Brassicaceae plants to complete the combined remediation of soil.

[0014] Further, in the step S1, the preparation method of the modified pine cone powder is as follows: wash the pine cone, dry at 45-50℃, crush and grind through a 60-mesh sieve to obtain pine cone powder, completely immerse the pine cone powder in a nitric acid solution for 10-12h, filter out the pine cone powder, dry at 55-60℃, then completely immerse the pine cone powder in a potassium hydroxide solution, heat to 80-85℃, and then immerse for 8-10h, filter out the pine cone powder, and then dry at 55-60℃ to obtain modified pine cone powder.

[0015] Description: By modifying the surface of pine cone powder, the roughness of the surface is increased, which can load more metal nanoparticles, and at the same time, it can be compounded with geopolymer, thereby improving the degradation and adsorption of biomass charcoal.

[0016] Further, the molar concentration of the nitric acid solution is 2-4M, and the molar concentration of the potassium hydroxide solution is 5-6M.

[0017] Description: The concentration of the nitric acid solution and the potassium hydroxide solution is preferably selected to modify the pine cone powder with the least raw materials.

[0018] Further, in step S1, the metakaolin is passed through an 80-mesh sieve.

[0019] Description: By adding metakaolin as a raw material for geopolymer and biomass charcoal, the modification of biomass charcoal is completed, and the modified biomass charcoal has good chemical stability, prolongs the adsorption time, and increases the adsorption capacity.

[0020] Further, in step S1-1, the amount of water added when dissolving is 2-3 times the total weight of the modified pine cone powder, metakaolin, and FeSO4·7H2O powder, the stirring speed is 150-200rpm, the drying temperature is 60-70℃, the mass concentration of the Na2SiO3 solution is 30-40%, and the molar ratio of SiO2 to Na2O in the Na2SiO3 solution is 1:1.

[0021] Description: By optimizing the preparation parameters of the modified biomass charcoal for cultivation, a modified biomass charcoal with good adsorption performance for cultivation is prepared, and the plants cultivated by the biomass charcoal are tightly combined with the biomass charcoal through their developed fibrous root system structure, thereby greatly absorbing pollutants and effectively avoiding the collapse of the pore structure at the initial stage of adsorbing pollutants, and having strong stress resistance.

[0022] Further, in step S1-2, the amount of water added when dissolving is 2-3 times the total weight of the modified pine cone powder, metakaolin, and CuSO4·5H2O powder, the stirring speed is 150-200rpm, the drying temperature is 60-70℃, the mass concentration of the Na2SiO3 solution is 30-40%, and the molar ratio of SiO2 to Na2O in the Na2SiO3 solution is 1:1.

[0023] Description: By optimizing the preparation parameters of the modified biomass charcoal for cultivation, a modified biomass charcoal with good adsorption performance for cultivation is prepared, and the plants cultivated by the biomass charcoal are tightly combined with the biomass charcoal through their developed fibrous root system structure, thereby greatly absorbing pollutants and effectively avoiding the collapse of the pore structure at the initial stage of adsorbing pollutants, and having strong stress resistance.

[0024] Further, the depth of the culture container in the step S2 is 8-10 cm, and the stirring depth of the modified biomass charcoal for cultivation is 5-8 cm.

[0025] Description: By optimizing the stirring depth of the modified biomass charcoal for cultivation, the plant roots after cultivation can be attached to the modified biomass charcoal for cultivation.

[0026] Further, the height of the ryegrass seedlings in the step S3 is 6-12 cm.

[0027] Description: By optimizing the height of the ryegrass seedlings, the root development can be ensured to be good.

[0028] Further, the amount of the modified biomass charcoal for planting in the step S4 is 4-5 kg / m 2 , the amount of the persulfate PMS is 4-6 kg / m 2 , the stirring depth is 10-20 cm, the space to be sowed is reserved between every two ryegrass seedlings, the remaining soil in the culture container is stirred into the space to be sowed, the stirring amount is 2-3 kg / m 2 , the stirring depth is 10-20 cm, the space to be sowed is 15-20*15-20 cm, the cruciferous plant seeds are sowed into the space to be sowed, and the water-soil ratio is maintained to be 0.4-0.5.

[0029] Description: By optimizing the specific parameters during the soil joint repair, the two different modified biomass charcoals can be more suitable for each other.

[0030] Still further, the cruciferous plant seeds in the step S4 are rape seeds.

[0031] Description: By optimizing the plant species for intercropping, the yield of the two plants can be improved.

[0032] The beneficial effects of the present application are:

[0033] (1) The method for repairing polycyclic aromatic hydrocarbon contaminated soil by the biomass charcoal joint plant cooperation of the present application can maximize the adsorption effect of the two different modified biomass charcoals by preparing the two different modified biomass charcoals and using them in different situations, wherein the modified biomass charcoal for cultivation is used for cultivating plants in the early stage, has a high geopolymer content, a relatively dense structure and is not easy to collapse, is beneficial to being attached to the roots, and is more suitable for developed roots to degrade pollutants; the modified biomass charcoal for planting is used for direct planting, has a low geopolymer content, increases the biomass charcoal content, loosens the dense structure of the geopolymer, increases the specific surface area and electron transfer capacity of the material, and is more suitable for degrading soil pollutants when the roots are not developed in the early stage of seed growth and development, and the two are used in different situations to maximize their respective functions.

[0034] (2) The method for remediating polycyclic aromatic hydrocarbon contaminated soil by biomass carbon combined with plants synergistically according to the application is prepared by compounding biomass carbon and geopolymer, and loading Fe and Cu on the two modified biomass carbons respectively. Metal nanoparticles can inhibit the growth of geopolymer skeleton, produce more cracks, improve the adsorption capacity, and at the same time can produce a synergistic effect between the two modified biomass carbons, produce redox cycle in the soil, and have better activation ability for PMS than single modified biomass carbon.

[0035] (3) The method for remediating polycyclic aromatic hydrocarbon contaminated soil by biomass carbon combined with plants synergistically according to the application is prepared by modifying the surface of pine cone powder, increasing the roughness of the surface, loading more metal nanoparticles, and compounding with geopolymer, thereby improving the degradation and adsorption of biomass carbon. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a flow chart of the method for remediating polycyclic aromatic hydrocarbon contaminated soil by biomass carbon combined with plants synergistically according to the application;

[0037] Figure 2 is the removal rate of polycyclic aromatic hydrocarbons in soil by the modified biomass carbon for cultivation and the modified biomass carbon for release prepared in Examples 1-3 in Example 1. DETAILED DESCRIPTION

[0038] Example 1

[0039] The method for remediating polycyclic aromatic hydrocarbon contaminated soil by biomass carbon combined with plants synergistically, comprising the following steps:

[0040] S1, modified biomass carbon preparation:

[0041] S1-1, preparation of modified biomass carbon for cultivation: metakaolin is passed through an 80 mesh sieve, and the modified pine cone powder, metakaolin and FeSO4·7H2O powder are mixed in a mass ratio of 1:2:4.3, dissolved and stirred with water, and dried to obtain a first premixed powder. The first premixed powder is added to a Na2SiO3 solution and stirred and mixed, and dried to obtain a first mixed powder. The first mixed powder is calcined at 725℃ for 2.5h under a nitrogen atmosphere to obtain the modified biomass carbon for cultivation. The amount of water added when dissolving is 2.5 times the total weight of the modified pine cone powder, metakaolin and FeSO4·7H2O powder, the stirring speed is 180rpm, the drying temperature is 65℃, the mass concentration of the Na2SiO3 solution is 35%, and the molar ratio of SiO2 to Na2O in the Na2SiO3 solution is 1:1.

[0042] S1-2, preparation of modified biomass charcoal for release: the metakaolin is passed through an 80-mesh sieve, the modified pine cone powder, metakaolin and CuSO4·5H2O powder are mixed in a mass ratio of 1:0.5:3.6, water is added for dissolution and stirring, and the second premixed powder is obtained after drying. The second premixed powder is added to the Na2SiO3 solution and stirred to mix, and the second mixed powder is obtained after drying. The second mixed powder is calcined at 720°C for 2.5h under a nitrogen atmosphere to obtain the modified biomass charcoal for release. The amount of water added for dissolution is 2.5 times the total weight of the modified pine cone powder, metakaolin and CuSO4·5H2O powder. The stirring speeds in the two stirring processes are both 170rpm. The drying temperatures in the two drying processes are both 65°C. The mass concentration of the Na2SiO3 solution is 35%. The molar ratio of SiO2 to Na2O in the Na2SiO3 solution is 1:1.

[0043] The preparation method of the modified pine cone powder is as follows: the pine cone is washed and dried at 47°C, then ground and sieved through a 60-mesh sieve to obtain pine cone powder. The pine cone powder is completely immersed in a nitric acid solution for 11h, then filtered and taken out for drying at 58°C. Subsequently, the pine cone powder is completely immersed in a potassium hydroxide solution, heated to 83°C and then immersed for 9h. After filtration, the pine cone powder is taken out and dried at 56°C to obtain the modified pine cone powder. The molar concentration of the nitric acid solution is 3M. The molar concentration of the potassium hydroxide solution is 5M.

[0044] S2, preparation of cultivation soil: the uncontaminated soil after crushing is placed in a culture container, and the modified biomass charcoal for cultivation is stirred in. The mass ratio of the modified biomass charcoal for cultivation to the uncontaminated soil is 1:500, and the cultivation soil is obtained. The depth of the culture container is 10cm, and the stirring depth of the modified biomass charcoal for cultivation is 8cm.

[0045] S3, cultivation of remediation plants: ryegrass seeds are scattered into the cultivation soil for cultivation, and the ryegrass seedlings are obtained. The height of the ryegrass seedlings is 6cm.

[0046] S4, soil joint remediation: the modified biomass charcoal for release and potassium peroxymonosulfate are stirred into the polycyclic aromatic hydrocarbon contaminated soil to be treated. The ryegrass seedlings are transplanted into the polycyclic aromatic hydrocarbon contaminated soil and intercropped with cruciferous plants to complete the soil joint remediation. The release amount of the modified biomass charcoal for release is 4kg / m 2 , the release amount of potassium peroxymonosulfate is 4kg / m 2 , the stirring depth is 10cm, and the reserved space for sowing is left between every two ryegrass seedlings. The remaining cultivation soil in the culture container is stirred into the space for sowing in an amount of 2kg / m 2 , and the stirring depth is 10cm. The space for sowing is 15*15cm, rape seeds are scattered into the space for sowing, and the water-soil ratio is maintained at 0.4.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is that:

[0049] S1-1, preparation of modified biomass charcoal for cultivation: the modified pine tower powder, metakaolin, FeSO4·7H2O powder were mixed according to the mass ratio of 1:2:4, dissolved and stirred with water, and the first premixed powder was obtained after drying. The first premixed powder was added to the Na2SiO3 solution and stirred to mix, and the first mixed powder was obtained after drying. The first mixed powder was calcined at 700℃ for 2h under nitrogen atmosphere to obtain modified biomass charcoal for cultivation. The amount of water added during dissolution was 2 times the total weight of modified pine tower powder, metakaolin and FeSO4·7H2O powder, the stirring speed was 150rpm, the drying temperature was 60℃, the mass concentration of Na2SiO3 solution was 30%, and the molar ratio of SiO2 to Na2O in Na2SiO3 solution was 1:1.

[0050] S1-2, preparation of modified biomass charcoal for release: the modified pine tower powder, metakaolin, CuSO4·5H2O powder were mixed according to the mass ratio of 1:0.5:3, dissolved and stirred with water, and the second premixed powder was obtained after drying. The second premixed powder was added to the Na2SiO3 solution and stirred to mix, and the second mixed powder was obtained after drying. The second mixed powder was calcined at 700℃ for 2h under nitrogen atmosphere to obtain modified biomass charcoal for release. The amount of water added during dissolution was 2 times the total weight of modified pine tower powder, metakaolin and CuSO4·5H2O powder, the stirring speed was 150rpm, the drying temperature was 60℃, the mass concentration of Na2SiO3 solution was 30%, and the molar ratio of SiO2 to Na2O in Na2SiO3 solution was 1:1.

[0051] Example 3

[0052] The difference between this embodiment and embodiment 1 is that:

[0053] S1-1, preparation of modified biomass charcoal for cultivation: the modified pine tower powder, metakaolin, FeSO4·7H2O powder were mixed according to the mass ratio of 1:2:5, dissolved and stirred with water, and the first premixed powder was obtained after drying. The first premixed powder was added to the Na2SiO3 solution and stirred to mix, and the first mixed powder was obtained after drying. The first mixed powder was calcined at 750℃ for 3h under nitrogen atmosphere to obtain modified biomass charcoal for cultivation. The amount of water added during dissolution was 3 times the total weight of modified pine tower powder, metakaolin and FeSO4·7H2O powder, the stirring speed was 200rpm, the drying temperature was 70℃, the mass concentration of Na2SiO3 solution was 40%, and the molar ratio of SiO2 to Na2O in Na2SiO3 solution was 1:1.

[0054] S1-2, modified biomass carbon for release preparation: metakaolin is passed through an 80-mesh sieve, modified pine cone powder, metakaolin, CuSO4·5H2O powder are mixed according to a mass ratio of 1:0.5:4, water is added for dissolution and stirring, and the second premixed powder is obtained after drying. The second mixed powder is added to the Na2SiO3 solution and stirred, and the second mixed powder is obtained after drying. The second mixed powder is calcined at 750℃ for 3h under nitrogen atmosphere to obtain the modified biomass carbon for release. The amount of water added during dissolution is 3 times the total weight of the modified pine cone powder, metakaolin and CuSO4·5H2O powder. The stirring speed is 200rpm for two times, and the drying temperature is 70℃ for two times. The mass concentration of Na2SiO3 solution is 40%, and the molar ratio of SiO2 to Na2O in Na2SiO3 solution is 1:1.

[0055] In Examples 1-3, the most important influencing factors on the final performance of the modified biomass carbon for cultivation and the modified biomass carbon for release are the mass ratio of modified pine cone powder, metakaolin and FeSO4·7H2O powder, and the mass ratio of modified pine cone powder, metakaolin and CuSO4·5H2O powder. Other parameters are within the reasonable range given by the present application and are adjusted conventionally. Therefore, in Experimental Example 1, we focus on the discussion of these two influencing factors.

[0056] Example 4

[0057] The difference between this example and Example 1 is:

[0058] The preparation method of the modified pine cone powder is: the pine cone is washed and dried at 45℃, then ground and sieved through a 60-mesh sieve to obtain pine cone powder. The pine cone powder is completely immersed in nitric acid solution for 10h, then filtered and the pine cone powder is taken out and dried at 55℃. Then it is completely immersed in potassium hydroxide solution, heated to 80℃ and immersed for 8h, then filtered and the pine cone powder is taken out and dried at 55℃ to obtain the modified pine cone powder. The molar concentration of the nitric acid solution is 2M, and the molar concentration of the potassium hydroxide solution is 5M.

[0059] Example 5

[0060] The difference between this example and Example 1 is:

[0061] The preparation method of the modified pine cone powder is: the pine cone is washed and dried at 50℃, then ground and sieved through a 60-mesh sieve to obtain pine cone powder. The pine cone powder is completely immersed in nitric acid solution for 12h, then filtered and the pine cone powder is taken out and dried at 60℃. Then it is completely immersed in potassium hydroxide solution, heated to 85℃ and immersed for 10h, then filtered and the pine cone powder is taken out and dried at 60℃ to obtain the modified pine cone powder. The molar concentration of the nitric acid solution is 4M, and the molar concentration of the potassium hydroxide solution is 6M.

[0062] Note: The parameter adjustment in Examples 1, 4 and 5 is a conventional adjustment within the reasonable range given by the present application, and the method selected from any of the examples can achieve the modification of pine cone powder.

[0063] Example 6

[0064] The difference between this embodiment and Example 1 is that:

[0065] S2, preparation of the cultivation soil: the crushed non-polluted soil is placed in a culture container, and the cultivation modified biomass charcoal is stirred in, the mass ratio of the cultivation modified biomass charcoal to the non-polluted soil is 1:600, to obtain the cultivation soil, the depth of the culture container is 10cm, and the stirring depth of the cultivation modified biomass charcoal is 7cm.

[0066] Example 7

[0067] The difference between this embodiment and Example 1 is that:

[0068] S2, preparation of the cultivation soil: the crushed non-polluted soil is placed in a culture container, and the cultivation modified biomass charcoal is stirred in, the mass ratio of the cultivation modified biomass charcoal to the non-polluted soil is 1:700, to obtain the cultivation soil, the depth of the culture container is 9cm, and the stirring depth of the cultivation modified biomass charcoal is 7cm.

[0069] Example 8

[0070] The difference between this embodiment and Example 1 is that:

[0071] S2, preparation of the cultivation soil: the crushed non-polluted soil is placed in a culture container, and the cultivation modified biomass charcoal is stirred in, the mass ratio of the cultivation modified biomass charcoal to the non-polluted soil is 1:800, to obtain the cultivation soil, the depth of the culture container is 9cm, and the stirring depth of the cultivation modified biomass charcoal is 6cm.

[0072] Example 9

[0073] The difference between this embodiment and Example 1 is that:

[0074] S2, preparation of the cultivation soil: the crushed non-polluted soil is placed in a culture container, and the cultivation modified biomass charcoal is stirred in, the mass ratio of the cultivation modified biomass charcoal to the non-polluted soil is 1:900, to obtain the cultivation soil, the depth of the culture container is 8cm, and the stirring depth of the cultivation modified biomass charcoal is 5cm.

[0075] Example 10

[0076] The difference between this embodiment and Example 1 is that:

[0077] S2, preparation of the cultivation soil: the non-polluted soil after crushing was placed in a culture container, and the modified biomass charcoal for cultivation was stirred in, the mass ratio of the modified biomass charcoal for cultivation to the non-polluted soil was 1:1000, the cultivation soil was obtained, the depth of the culture container was 8 cm, and the stirring depth of the modified biomass charcoal for cultivation was 5 cm.

[0078] Example 11

[0079] The difference between this example and Example 1 is that:

[0080] S3, cultivation of the repair plant: the ryegrass seeds were scattered into the cultivation soil for cultivation, and the ryegrass seedlings were obtained, the height of the ryegrass seedlings was 8 cm.

[0081] Example 12

[0082] The difference between this example and Example 1 is that:

[0083] S3, cultivation of the repair plant: the ryegrass seeds were scattered into the cultivation soil for cultivation, and the ryegrass seedlings were obtained, the height of the ryegrass seedlings was 10 cm.

[0084] Example 13

[0085] The difference between this example and Example 1 is that:

[0086] S3, cultivation of the repair plant: the ryegrass seeds were scattered into the cultivation soil for cultivation, and the ryegrass seedlings were obtained, the height of the ryegrass seedlings was 12 cm.

[0087] Example 14

[0088] The difference between this example and Example 1 is that:

[0089] S4, joint repair of the soil: the modified biomass charcoal for delivery and potassium peroxymonosulfate were stirred into the polycyclic aromatic hydrocarbon contaminated soil to be treated, the ryegrass seedlings were transplanted into the polycyclic aromatic hydrocarbon contaminated soil, and the Brassicaceae plant was intercropped, the joint repair of the soil was completed, the delivery amount of the modified biomass charcoal for delivery was 4.5 kg / m 2 , the delivery amount of the potassium peroxymonosulfate was 5 kg / m 2 , the stirring depth was 15 cm, the space to be sowed was reserved between every two ryegrass seedlings, the remaining cultivation soil in the culture container was stirred into the space to be sowed, the stirring amount was 2.5 kg / m 2 , the stirring depth was 15 cm, the space to be sowed was 17*17 cm, the rape seeds were scattered into the space to be sowed, and the water-soil ratio was maintained at 0.45.

[0090] Example 15

[0091] The difference between this example and Example 1 is that:

[0092] S4, soil joint remediation: modified biomass charcoal and potassium peroxymonosulfate are mixed and added to the polycyclic aromatic hydrocarbon contaminated soil to be treated, ryegrass seedlings are transplanted into the polycyclic aromatic hydrocarbon contaminated soil, and the Brassicaceae is intercropped, to complete the soil joint remediation, the amount of modified biomass charcoal added is 5 kg / m 2 , the amount of potassium peroxymonosulfate added is 6 kg / m 2 , the mixing depth is 20 cm, the space to be seeded is reserved between every two ryegrass seedlings, the remaining culture soil in the culture container is mixed into the space to be seeded, the mixing amount is 3 kg / m 2 , the mixing depth is 20 cm, the space to be seeded is 20*20 cm, rapeseed is scattered into the space to be seeded, and the water-soil ratio is maintained at 0.5.

[0093] Note: in step S4, different methods in example 1 415 are selected, in which the amount of modified biomass charcoal added and the amount of potassium peroxymonosulfate added are the final main influencing factors, and in actual use, the amount of modified biomass charcoal added and the amount of potassium peroxymonosulfate added can be appropriately increased or decreased according to the severity of soil pollution, so as to achieve the best economic benefit.

[0094] Experimental example 1

[0095] The culture modified biomass charcoal and the modified biomass charcoal for adding prepared in examples 1-3 are taken, and their removal rates of polycyclic aromatic hydrocarbons in soil are respectively studied by indoor test method. 5 g of naphthalene-containing contaminated soil is taken, 3 mL of water is added, 10 mg of culture modified biomass charcoal and modified biomass charcoal for adding prepared in examples 1-3 is respectively added, 10 mg of potassium peroxymonosulfate is added, 25 mL of acetone and dichloromethane solution with a volume ratio of 1:1 is added, naphthalene is extracted and filtered, and then the concentration of naphthalene is determined by liquid chromatography, and the removal rate is calculated as Figure 2 shown.

[0096] It can be seen that in examples 1-3, the adsorption capacity of the culture modified biomass charcoal and the modified biomass charcoal for adding prepared by increasing the addition amount of FeSO4·7H2O and CuSO4·5H2O shows a trend of first increasing and then decreasing, which shows that the addition of metal elements has good activation capacity for PMS, but too much addition of Fe and Cu will occupy too many active adsorption sites of the biomass charcoal, thereby reducing the adsorption rate of naphthalene.

[0097] Experimental example 2

[0098] Actual high molecular weight fluoranthene contaminated soil was treated according to the method in Examples 1, 6-10, and comparative examples were compared. The difference between Comparative Example 1 and Example 1 is that the modified biomass carbon for cultivation and the modified biomass carbon for release were directly mixed and added to the contaminated soil, and steps S2-S4 were omitted. The difference between Comparative Example 2 and Example 1 is that the modified biomass carbon for cultivation was directly added to the contaminated soil, and steps S2-S4 were omitted. The difference between Comparative Example 3 and Example 1 is that the modified biomass carbon for release was directly added to the contaminated soil, and steps S2-S4 were omitted. The results are shown in Table 1.

[0099] Table 1: High molecular weight fluoranthene removal rate in each case

[0100]

[0101]

[0102] It can be seen that when the modified biomass carbon for cultivation or the modified biomass carbon for release is used alone for soil pollution treatment, the high molecular weight fluoranthene removal rate is not ideal, but when the modified biomass carbon for cultivation and the modified biomass carbon for release are used together, the high molecular weight fluoranthene removal rate in the soil can be improved, which shows that there is a certain mutual promotion relationship between the two, and the two modified biomass carbons can produce a synergistic effect, and a redox cycle can be generated in the soil. Compared with a single modified biomass carbon, the modified biomass carbon has better activation ability for PMS.

[0103] After using the method in the present application, the high molecular weight fluoranthene removal rate in the soil can be further improved, which also shows that the modified biomass carbon for cultivation is used for pre-cultivation of plants, has a high content of geopolymer, a relatively dense structure and is not easy to collapse, is beneficial to adhere to the root system, and is more suitable for developed root system and simultaneous pollutant degradation. The modified biomass carbon for release is directly released, has a low content of geopolymer, increases the content of biomass carbon, loosens the dense structure of geopolymer, increases the specific surface area and electron transfer capacity, and is more suitable for soil pollutant degradation when the root system is not developed in the early stage of seed growth and development.

[0104] Increasing the mass ratio of the modified biomass carbon for cultivation to the uncontaminated soil can generally improve the high molecular weight fluoranthene removal rate in the soil, but too many iron nanoparticles loaded on the surface of the biomass carbon also cause partial pore blockage, which slightly reduces the high molecular weight fluoranthene removal rate in the soil. Therefore, in addition to increasing the mass ratio of the modified biomass carbon for cultivation to the uncontaminated soil, the height of the ryegrass seedlings in Examples 11-13 should also be considered. When the height of the ryegrass seedlings is higher, the root system is more developed, and more modified biomass carbon for cultivation is attached.

Claims

1. A method for the biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, characterized in that, Includes the following steps: S1. Preparation of modified biochar: S1-1 Preparation of modified biochar for cultivation: Modified pine cone powder, metakaolin, and FeSO4·7H2O powder are mixed in a mass ratio of 1:2:4~5, dissolved in water and stirred, and dried to obtain a first premixed powder. The first premixed powder is added to Na2SiO3 solution and stirred and mixed, and dried to obtain a first mixed powder. The first mixed powder is calcined at 700~750℃ for 2~3h under a nitrogen atmosphere to obtain modified biochar for cultivation. S1-2 Preparation of modified biochar for application: Modified pine cone powder, metakaolin, and CuSO4·5H2O powder are mixed in a mass ratio of 1:0.5:3~4, dissolved in water and stirred. After drying, a second premixed powder is obtained. The second premixed powder is added to Na2SiO3 solution and stirred and mixed. After drying, a second mixed powder is obtained. The second mixed powder is calcined at 700~750℃ for 2~3h under a nitrogen atmosphere to obtain modified biochar for application. S2. Preparation of cultivation soil: Place the pulverized pollution-free soil in a cultivation container and mix in the modified biochar for cultivation. The mass ratio of the modified biochar for cultivation to the pollution-free soil is 1:500~1000 to obtain the cultivation soil. S3. Repairing plant cultivation: Sprinkle ryegrass seeds into the cultivation soil and cultivate them to obtain ryegrass seedlings; S4. Soil remediation: The modified biochar and persulfate PMS are mixed into the polycyclic aromatic hydrocarbon (PAH) contaminated soil to be treated. The ryegrass seedlings are then transplanted into the PAH contaminated soil and intercropped with cruciferous plants to complete the soil remediation.

2. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In step S1, the modified pine cone powder is prepared as follows: the pine cones are washed and dried at 45-50°C, then pulverized and ground through a 60-mesh sieve to obtain pine cone powder. The pine cone powder is completely immersed in nitric acid solution for 10-12 hours, filtered, and then dried at 55-60°C. Subsequently, it is completely immersed in potassium hydroxide solution, heated to 80-85°C, and soaked for 8-10 hours. After filtration, the pine cone powder is dried at 55-60°C to obtain modified pine cone powder.

3. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 2, characterized in that, The molar concentration of the nitric acid solution is 2-4 mol / L, and the molar concentration of the potassium hydroxide solution is 5-6 mol / L.

4. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In step S1, the metakaolin is passed through an 80-mesh sieve.

5. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In step S1-1, the amount of water added during dissolution is 2 to 3 times the total weight of the modified pine cone powder, metakaolin, and FeSO4·7H2O powder. The stirring speed is 150 to 200 rpm for both times, and the drying temperature is 60 to 70°C for both times. The mass concentration of the Na2SiO3 solution is 30 to 40%, and the molar ratio of SiO2 to Na2O in the Na2SiO3 solution is 1:

1.

6. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In steps S1-2, the amount of water added during dissolution is 2 to 3 times the total weight of the modified pine cone powder, metakaolin, and CuSO4·5H2O powder. The stirring speed is 150 to 200 rpm for both steps, and the drying temperature is 60 to 70°C for both steps. The mass concentration of the Na2SiO3 solution is 30 to 40%, and the molar ratio of SiO2 to Na2O in the Na2SiO3 solution is 1:

1.

7. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In step S2, the depth of the culture container is 8-10 cm, and the depth of the modified biochar for cultivation is 5-8 cm.

8. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In step S3, the height of the ryegrass seedlings is 6-12cm.

9. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 1, characterized in that, In step S4, the amount of modified biochar added is 4-5 kg / m³. 2 The dosage of persulfate PMS is 4-6 kg / m³. 2 The soil should be mixed to a depth of 10-20cm, leaving space between every two ryegrass seedlings for sowing. The remaining potting soil in the culture container should be mixed into the sowing space at a rate of 2-3 kg / m². 2 Mix the seeds to a depth of 10-20cm, and prepare a sowing space of 15-20cm x 15-20cm. Sow cruciferous seeds into the sowing space and maintain a water-to-soil ratio of 0.4-0.

5.

10. The method for biomass carbon-based phytoremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil according to claim 9, characterized in that, The cruciferous plant seeds mentioned in step S4 are rapeseed seeds.

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