Remediation composition for polycyclic aromatic hydrocarbons contaminated soil and its application

Abstract

The present invention provides a remediation composition for polycyclic aromatic hydrocarbon (PAH)-contaminated soil and its application. The remediation composition comprises persulfate, peroxide, a free radical initiator, and a cosolvent. By adding the initiator and cosolvent to a dual oxidant system comprising peroxide and persulfate, the use of catalysts and chelating agents is avoided while the degradation rate of PAHs in the soil is increased. It is believed that the addition of the cosolvent facilitates the desorption of pollutants, while the addition of the initiator can stimulate the persulfate and calcium peroxide to generate active free radicals, generating SO4· ‑ They stimulate each other and work together to achieve the purpose of repairing soil contaminated by organic matter.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic matter contaminated soil remediation, and in particular relates to a remediation composition for polycyclic aromatic hydrocarbons contaminated soil and an application thereof. Background Art

[0002] Organic pollutants and their harmful effects on human health and ecosystems are increasingly recognized. Countries such as the United States, the United Kingdom, Germany, and the Netherlands have prioritized soil pollution control on par with air and water pollution, and have developed government-level remediation programs. Germany invested approximately $6 billion in soil cleanup as early as 1995, and the United States invested tens to hundreds of billions of dollars in soil restoration in the 1990s. However, my country currently lacks sufficient attention to the severity of soil pollution and the urgency of its remediation efforts. Furthermore, due to regional variations in soil quality, the complexity of ecosystems, and soil immobility, soil pollution is more complex and challenging to control than water or air pollution. Therefore, there is an urgent need to develop economically viable soil remediation technologies that are highly efficient at degrading recalcitrant organic pollutants.

[0003] Currently, there are numerous reports abroad on the degradation of organic pollutants in soil using single oxidants, such as peroxides, persulfates, and permanganates. These methods can achieve slow free radical release, high degradation efficiency, and long action times, and exhibit good degradation effects on a wide range of organic pollutants. Persulfate has attracted widespread attention due to its wide pH range, environmental friendliness, and long underground transport distance. Single oxidant systems, due to their inherent limitations, have limited ability to remove recalcitrant pollutants. A mixture of hydrogen peroxide and sodium persulfate may possess stronger oxidative capacity. Reports on dual oxidants are relatively rare, primarily focusing on hydrogen peroxide and persulfate dual oxidant systems. While these systems demonstrate good degradation effects on organic pollutants, they face certain challenges in practical application, such as the storage and transportation of hydrogen peroxide, as well as its rapid release rate and short effective action time during organic matter degradation.

[0004] Calcium peroxide is reportedly a versatile, safe, solid inorganic peroxide that slowly releases hydrogen peroxide to produce ·OH in a humid environment. It is considered solid hydrogen peroxide and is well-suited for use in environmental remediation. The dual oxidant system, composed of persulfate and calcium peroxide, is less sensitive to environmental changes and exhibits high oxidative activity against a variety of organic pollutants. The synergistic effect between the two oxidants can also promote the oxidation of difficult-to-degrade organic pollutants, thereby improving degradation efficiency. This provides support for the development of technologies for remediating organically contaminated soils.

[0005] Polycyclic aromatic hydrocarbons (PAHs) are a type of difficult-to-degrade soil organic pollutants that are carcinogenic, teratogenic, and mutagenic. The PAH-contaminated soil remediation agents used in existing technologies include oxidants, catalysts, and chelating agents. Oxidants are mainly peroxides and persulfates, catalysts are mainly divalent iron salts, and chelating agents include citric acid, EDTA, and the like. Regardless of whether a single oxidant or a dual oxidant system composed of different oxidants is used, the remediation of PAHs in the soil suffers from problems such as low degradation efficiency and toxic and harmful degradation products. Furthermore, the addition of catalysts and chelating agents increases the remediation cost, which is not conducive to the use of actual contaminated sites.

[0006] It can be seen from this that it is necessary to improve the existing oxidant system used for the remediation of organic contaminated soil and develop a petroleum hydrocarbon contaminated soil remediation method with high remediation efficiency, low remediation cost and environmental friendliness. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to overcome the problems of low degradation rate and high remediation cost of polycyclic aromatic hydrocarbons in soil in the prior art, and to provide a remediation composition for polycyclic aromatic hydrocarbons-contaminated soil and its application. The remediation composition of the present invention can increase the degradation rate of polycyclic aromatic hydrocarbons in contaminated soil.

[0008] The objectives of the present invention are achieved through the following technical solutions.

[0009] In a first aspect, the present invention provides a remediation composition for polycyclic aromatic hydrocarbon-contaminated soil, wherein the remediation composition comprises persulfate, peroxide, a free radical initiator and a cosolvent.

[0010] In the present invention, by adding an initiator and a cosolvent to the dual oxidant system comprising peroxide and persulfate, the use of a catalyst and a chelating agent is avoided and the degradation rate of polycyclic aromatic hydrocarbons in soil is increased. Without wishing to be bound by theory, it is believed that the addition of the cosolvent facilitates the desorption of pollutants, and the addition of the initiator can stimulate the persulfate and calcium peroxide to generate active free radicals, generating SO4· - They stimulate each other and work together to achieve the purpose of repairing soil contaminated by organic matter.

[0011] According to the repair composition provided by the present invention, the repair composition does not include a catalyst and / or a chelating agent.

[0012] According to the repair composition provided by the present invention, the peroxide is a solid inorganic peroxide. In some embodiments, the peroxide is calcium peroxide and / or magnesium peroxide.

[0013] According to the repair composition provided by the present invention, the persulfate is selected from at least one of sodium persulfate, potassium persulfate and ammonium persulfate. In some embodiments, the persulfate is sodium persulfate and / or potassium persulfate.

[0014] According to the repair composition provided by the present invention, the mass ratio of the peroxide to the persulfate is 1:2 to 8; in some embodiments, it is 1:3 to 6.

[0015] According to the repair composition provided by the present invention, the free radical initiator is a water-soluble azo initiator. Examples of water-soluble azo initiators suitable for use in the present invention include, but are not limited to, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azobiscyanovaleric acid, and azobisisopropylimidazoline.

[0016] According to the repair composition provided by the present invention, the ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator can be 1:0.002-0.01, preferably 1:0.005-0.01, and more preferably 1:0.005-0.008.

[0017] In the repair composition provided by the present invention, the cosolvent is a monohydric alcohol or dihydric alcohol having 1 to 6 carbon atoms, preferably a monohydric alcohol or dihydric alcohol having 2 to 4 carbon atoms. Examples of cosolvents suitable for use in the present invention include, but are not limited to, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol. In some embodiments, the cosolvent is ethanol and / or isopropanol.

[0018] According to the repair composition provided by the present invention, the amount of the co-solvent is 50 to 200 ml, preferably 100 to 150 ml, relative to 100 g of the peroxide and the persulfate.

[0019] In a second aspect, the present invention provides use of the remediation composition in remediating polycyclic aromatic hydrocarbons-contaminated soil.

[0020] According to the application provided by the present invention, the polycyclic aromatic hydrocarbons refer to aromatic hydrocarbons containing two or more benzene rings. The polycyclic aromatic hydrocarbon content in polycyclic aromatic hydrocarbon-contaminated soil is generally greater than the polycyclic aromatic hydrocarbon soil pollution risk screening value for Class II construction land specified in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)". For example, the polycyclic aromatic hydrocarbons are selected from at least one of naphthalene, phenanthrene, anthracene, pyrene, benzo[a]pyrene, and / or benzo[b]fluoranthene.

[0021] In the present invention, there are no specific requirements for the size of the PAH-contaminated soil to be remediated. Generally, smaller soil particle size allows for more complete contact, facilitating remediation. However, reducing soil particle size typically increases treatment costs. In some embodiments, the PAH-contaminated soil has a particle size of 2 mm or less.

[0022] According to the application provided by the present invention, the application comprises the following steps:

[0023] S100, adding a first portion of water and a cosolvent to the polycyclic aromatic hydrocarbon contaminated soil, and mixing to obtain a first mixture;

[0024] S200, mixing the initiator, the persulfate and the second portion of water and heating the mixture to obtain a second solution;

[0025] S300 , mixing the peroxide, the first mixture obtained in step S100 and the second solution obtained in step S200 .

[0026] According to the application provided by the present invention, in step S100, the amount of the co-solvent used is 20 to 80 ml, preferably 40 to 60 ml, for example, 50 ml, per kilogram of the polycyclic aromatic hydrocarbons-contaminated soil; and / or, the amount of the first portion of water used is 3 kg to 5 kg per kilogram of the polycyclic aromatic hydrocarbons-contaminated soil.

[0027] According to the application provided by the present invention, the mixing time in step S100 is 1 to 3 hours, for example, 2 hours.

[0028] According to the application provided by the present invention, in step S200, the amount of the persulfate used is 5 g to 20 g per kilogram of the polycyclic aromatic hydrocarbons-contaminated soil.

[0029] According to the application provided by the present invention, in step S200, based on 1000 parts by weight of the peroxide and the persulfate, the added amount of the initiator is 5 to 8 parts by weight.

[0030] According to the application provided by the present invention, the mass ratio of the initiator to the second portion of water is 1:500-1500, preferably 1:800-1200, and more preferably 1:900-1100.

[0031] According to the application provided by the present invention, the heating temperature in step S200 is 50° C. to 65° C. At such a temperature, the initiator is conducive to exciting the persulfate to generate active free radicals.

[0032] According to the application provided by the present invention, the mixing treatment in step S300 is performed for 1 to 12 hours, preferably 6 to 10 hours; and / or the mixing treatment is performed at room temperature.

[0033] According to the application provided by the present invention, step S300 further comprises: performing solid-liquid separation after the mixing process. In the present invention, any method known in the art can be used for solid-liquid separation, and the present invention is not particular thereto.

[0034] The above raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0035] Compared with the prior art, the present invention has at least the following advantages:

[0036] (1) In the repair composition of the present invention, by adding a small amount of initiator, the use of catalysts and chelating agents can be avoided, and the decomposition products of the initiator are non-toxic, which can reduce the repair cost and avoid the impact of the catalyst and chelating agent on the soil structure after repair.

[0037] (2) The remediation method (application) provided by the present invention has a good remediation effect. The addition of a cosolvent is conducive to the desorption of pollutants, thereby improving the degradation efficiency. After the high-concentration PAH-contaminated soil is remediated by this method, the removal rate of PAHs can reach more than 90%. The content of various PAHs in the remediated soil is lower than the PAH soil pollution risk screening value for the second type of construction land specified in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)", which can meet the remediation requirements of PAH-contaminated soil around petroleum and petrochemical enterprises or abandoned plots.

[0038] (3) The addition of initiator can stimulate persulfate and peroxide to generate active free radicals, and the generated SO4· - The remediation composition and remediation method (application) of the present invention can degrade polycyclic aromatic hydrocarbons into small organic molecules or even completely mineralize them, without causing secondary pollution to the environment.

[0039] (4) The dual oxidant system not only improves the degradation efficiency of pollutants, but also converts refractory organic matter into easily degradable organic matter. In particular, solid inorganic peroxides can slowly release hydrogen peroxide during soil remediation, increasing the effective action time of the oxidant and fully exerting the oxidizing effect of the oxidant, thereby improving soil remediation efficiency and reducing remediation costs. Persulfate can generate free radicals over a wide pH range, making up for the low activity of peroxides under alkaline conditions. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0041] Preparation of contaminated soil samples:

[0042] (1) Collect soil from the 0-20 cm tillage layer, remove gravel and animal and plant debris from the soil, dry it at 200°C, and pass it through a 2 mm sieve to obtain uncontaminated soil for later use.

[0043] (2) A certain amount of PAHs is dissolved in dichloromethane, and the prepared PAH / dichloromethane solution is added to the uncontaminated soil in the above step (1) under continuous stirring. After continuing to stir until uniform, the soil is placed in a fume hood to allow the solvent to evaporate naturally, thereby obtaining PAH-contaminated soil.

[0044] Contaminated soils of varying concentrations can be prepared based on the amount of added pollutants. The PAH levels in these prepared contaminated soils all exceeded the PAH soil contamination risk screening values ​​for Category II construction land as specified in the "Soil Environmental Quality Standards for Soil Pollution Risk Control for Construction Land." Based on this, the following remediation tests were conducted.

[0045] Example 1

[0046] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0047] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0048] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0049] Example 2

[0050] 10 g of naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 50 mL of water were added. The tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0051] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0052] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0053] Example 3

[0054] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0055] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.2 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.6 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0056] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0057] Example 4

[0058] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0059] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.5 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0060] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0061] Example 5

[0062] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0063] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 60°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0064] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0065] Example 6

[0066] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0067] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 10 hours.

[0068] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0069] Example 7

[0070] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 500 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0071] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0072] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0073] Example 8

[0074] Weigh 10 g of prepared benzo[a]pyrene-contaminated soil with a benzo[a]pyrene concentration of 30 ppm into a 50 mL centrifuge tube, add 0.5 mL of ethanol and 30 mL of water, place the tube on a rotary shaker, and rotate at room temperature for 2 hours to obtain a mixture of the cosolvent and soil.

[0075] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0076] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0077] Example 9

[0078] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of isopropanol and 30 mL of water were added. The tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0079] Weigh 0.002 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0080] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0081] Example 10

[0082] 10 g of the prepared naphthalene-contaminated soil with a naphthalene concentration of 300 ppm was weighed and placed in a 50 mL centrifuge tube. 0.5 mL of ethanol and 30 mL of water were added, and the tube was placed on a rotary shaker and rotated at room temperature for 2 hours to obtain a mixture of the cosolvent and the soil.

[0083] Weigh 0.0028 g of azobisisobutylamidine hydrochloride and 0.1 g of sodium persulfate and dissolve them in 2.8 mL of water to prepare a solution. Heat the solution to 50°C and then add it to the mixture of the above-mentioned cosolvent and soil. At the same time, add 0.3 g of calcium peroxide. After mixing evenly in a vortex mixer, place it on a rotary shaker and rotate it at room temperature for 6 hours.

[0084] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0085] Comparative Example 1

[0086] 10g of the prepared naphthalene-contaminated soil was weighed and placed in a 50mL centrifuge tube. The naphthalene concentration in the soil was 300ppm. 30mL of deionized water was added to the centrifuge tube, and the contaminated soil and deionized water were mixed using a vortex mixer. 0.1g of sodium persulfate, 0.3g of calcium peroxide, 0.3861g of ferrous sulfate, and 0.2671g of citric acid were then weighed and added to the centrifuge tube. After mixing in a vortex mixer, the tube was placed on a rotary shaker and rotated at room temperature for 6 hours.

[0087] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0088] Comparative Example 2

[0089] The naphthalene-contaminated soil was remediated using a method substantially the same as that in Example 1, except that ethanol was not used as a cosolvent.

[0090] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0091] Table 1 Experimental results (ppm)

[0092] Example pollutants Initial pollutant concentration Residual pollutant concentration Degradation rate (%) 1 Naphthalene 300 23 92.3 2 Naphthalene 300 20 93.3 3 Naphthalene 300 9 97 4 Naphthalene 300 21 93 5 Naphthalene 300 14 95.3 6 Naphthalene 300 17 94.3 7 Naphthalene 500 43 91.4 8 Benzo[a]pyrene 30 1.1 96.3 9 Naphthalene 300 25 91.7 10 Naphthalene 300 16 94.7 Comparative Example 1 Naphthalene 300 62 79.3 Comparative Example 2 Naphthalene 300 54 82.0

[0093] From the above results, it can be seen that the use of the remediation composition of the present invention, by adding a cosolvent and a small amount of initiator, without using a catalyst and a chelating agent, the dual oxidant system composed of calcium peroxide and sodium persulfate has a good remediation effect on polycyclic aromatic hydrocarbons contaminated soil. The degradation rate of polycyclic aromatic hydrocarbons in the soil is greater than 90%, and the content of polycyclic aromatic hydrocarbons in the soil after remediation is lower than the various polycyclic aromatic hydrocarbon soil pollution risk screening values ​​for the second category of construction land specified in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)", and has good application prospects.

[0094] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A composition for remediating soil contaminated with polycyclic aromatic hydrocarbons, wherein: The repair composition comprises persulfate, peroxide, a free radical initiator and a cosolvent; the mass ratio of the peroxide to the persulfate is 1:2-8, and the ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator is 1:0.002-0.01; the repair composition does not include a catalyst and / or a chelating agent; the polycyclic aromatic hydrocarbon is selected from at least one of naphthalene, phenanthrene, anthracene, pyrene, benzo[a]pyrene and / or benzo[b]fluoranthene; The peroxide is a solid inorganic peroxide; and the free radical initiator is a water-soluble azo initiator.

2. The repair composition according to claim 1, characterized in that The persulfate is selected from at least one of sodium persulfate, potassium persulfate and ammonium persulfate.

3. The repair composition according to claim 2, characterized in that The peroxide is calcium peroxide and / or magnesium peroxide; and / or, The persulfate is sodium persulfate and / or potassium persulfate.

4. The repair composition according to claim 1, characterized in that The mass ratio of the peroxide to the persulfate is 1:3-6.

5. The repair composition according to any one of claims 1 to 4, characterized in that The ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator is 1:0.005-0.

01.

6. The repair composition according to claim 5, characterized in that The free radical initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azobiscyanovaleric acid and azobisisopropylimidazoline; and / or The ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator is 1:0.005-0.

008.

7. The repair composition according to any one of claims 1 to 4, characterized in that The cosolvent is a monohydric alcohol or dihydric alcohol having 1 to 6 carbon atoms; and / or The amount of the co-solvent used is 50-200 ml relative to 100 g of the peroxide and the persulfate.

8. The repair composition according to claim 7, characterized in that The cosolvent is a monohydric alcohol or dihydric alcohol having 2 to 4 carbon atoms; and / or The amount of the co-solvent used is 100-150 ml relative to 100 g of the peroxide and the persulfate.

9. The repair composition according to claim 8, characterized in that The co-solvent is selected from at least one of ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, 1,3-propylene glycol and 1,4-butanediol.

10. Use of the remediation composition according to any one of claims 1 to 9 in remediating soil contaminated by polycyclic aromatic hydrocarbons.

11. The use according to claim 10, characterized in that The particle size of the polycyclic aromatic hydrocarbons-contaminated soil is less than 2 mm.

12. The use according to claim 10 or 11, characterized in that The application comprises the following steps: S100, adding a first portion of water and a cosolvent to the polycyclic aromatic hydrocarbon contaminated soil, and mixing to obtain a first mixture; S200, mixing the initiator, the persulfate and the second portion of water and heating the mixture to obtain a second solution; S300 , mixing the peroxide, the first mixture obtained in step S100 and the second solution obtained in step S200 .

13. The use according to claim 12, characterized in that In step S100, the amount of the co-solvent used is 20-80 ml per kilogram of the polycyclic aromatic hydrocarbon-contaminated soil; and / or, the amount of the first portion of water used is 3-5 kg ​​per kilogram of the polycyclic aromatic hydrocarbon-contaminated soil; and / or, the mixing time in step S100 is 1-3 hours.

14. The use according to claim 13, characterized in that In step S100, the amount of the co-solvent used is 40-60 ml per kilogram of the polycyclic aromatic hydrocarbons-contaminated soil.

15. The use according to claim 12, characterized in that In step S200, the amount of the persulfate used is 5 g to 20 g per kilogram of the polycyclic aromatic hydrocarbon-contaminated soil; and / or the mass ratio of the initiator to the second portion of water is 1:500 to 1500; and / or the heating temperature in step S200 is 50° C. to 65° C.

16. The use according to claim 15, characterized in that In step S200, the mass ratio of the initiator to the second portion of water is 1:800-1200.

17. The use according to claim 16, characterized in that In step S200, the mass ratio of the initiator to the second portion of water is 1:900-1100.

18. The use according to claim 12, characterized in that The mixing process in step S300 is performed for 1 to 12 hours; and / or the mixing process is performed at room temperature.

19. The use according to claim 18, characterized in that The mixing process in step S300 is performed for 6 to 10 hours.