Methods and applications for remediating contaminated soil

Abstract

This invention relates to the field of contaminated soil remediation technology, and discloses a method for remediating contaminated soil and its application. The method for remediating contaminated soil of this invention includes: (1) mixing contaminated soil with a first solvent to obtain a first mixture; (2) mixing a remediation agent with a second solvent to obtain a second mixture; and (3) contacting the first mixture and the second mixture under hypergravity conditions. The method of this invention can improve the degradation effect of organic pollutants, increase the remediation efficiency of contaminated soil, and reduce the amount of remediation agent used, remediation time, and remediation costs without causing secondary pollution to the environment.

Description

Technical Field

[0001] This invention relates to the field of contaminated soil remediation technology, specifically to methods for remediating contaminated soil and their applications. Background Technology

[0002] The harmful effects of petroleum hydrocarbons and other organic pollutants on human health and ecosystems are increasingly recognized. However, due to regional differences in soil, the complexity of ecosystems, and the immobility of soil, soil pollution is more complex and difficult to remediate than water or air pollution. Therefore, there is an urgent need to develop economically feasible soil remediation technologies with high degradation efficiency for recalcitrant petroleum hydrocarbons and other organic pollutants.

[0003] Currently, the main methods for remediating soil contaminated with petroleum hydrocarbons and other organic matter involve mixing remediation agents with the soil or injecting the remediation agents directly into the soil. One commonly used remediation agent is one that includes surfactants, sodium persulfate, citric acid, ferrous salts, and alkaline peroxides. However, while alkaline peroxides can avoid the soil acidification problems caused by sodium persulfate, the use of citric acid increases remediation costs, and citric acid also complexes with Fe... 2+ Activated sodium persulfate has a poor effect on the degradation of petroleum hydrocarbons in soil, with a degradation rate of less than 80%. In addition, currently used chemical remediation and bioremediation methods have the problems of large amounts of remediation agents (greater than 5%) and long remediation times (one month or even several months), respectively.

[0004] To enhance the degradation of organic pollutants in contaminated soil, methods mainly involve increasing the amount of oxidant, extending the reaction time, or utilizing the synergistic effect between multiple oxidants. However, even after such treatment, the concentration of residual organic pollutants in the contaminated soil remains high, indicating that the above methods have a limited effect on promoting the oxidative degradation of organic pollutants in the soil.

[0005] Therefore, it is necessary to improve existing methods for remediating organically contaminated soil and develop a method that is highly efficient, low-cost, and environmentally friendly. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low remediation efficiency due to poor removal rates of organic pollutants in organic-contaminated soil in existing technologies, and to provide a method for remediating contaminated soil and its application. This method can improve the degradation effect of organic pollutants, increase the remediation efficiency of contaminated soil, reduce the amount of remediation agent used, shorten the remediation time, reduce the remediation cost, and avoid causing secondary pollution to the environment.

[0007] The first aspect of this invention provides a method for remediating contaminated soil, the method comprising:

[0008] (1) The contaminated soil is mixed with a first solvent to obtain a first mixture;

[0009] (2) The repair agent is mixed with the second solvent to obtain a second mixture;

[0010] (3) The first mixture and the second mixture are brought into contact under hypergravity conditions.

[0011] A second aspect of the present invention provides the application of the method described above in reducing the content of organic pollutants in organically contaminated soil.

[0012] The beneficial effects of the present invention through the above technical solution include:

[0013] (1) The method of the present invention is applicable to different remediation agents and different kinds of organic pollutants in soil, and has the characteristics of being simple and efficient;

[0014] (2) After the organic pollutant soil is remediated using the method of the present invention, the organic pollutant removal rate is greater than 80%, and the content of various organic pollutants in the soil is lower than the screening value of soil pollution risk for Class II construction land as specified in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)" (GB 36600-2018), which can meet the remediation requirements of organic pollutant soil around operating enterprises such as petroleum and petrochemical plants or abandoned plots.

[0015] (3) The method of the present invention can improve the utilization efficiency of the repair agent, reduce the use of the repair agent, and reduce the repair cost;

[0016] (4) The remediation method of the present invention only requires the addition of a supergravity machine at the remediation site to achieve efficient degradation of organic pollutants. The required equipment is simple, easy to install and operate.

[0017] (5) Compared with traditional remediation methods, the remediation agent used in the method of the present invention does not require the addition of surfactants or solubilizers, and will not cause secondary pollution of soil;

[0018] (6) The inventors found in their research that mixing contaminated soil and remediation agent with the first solvent and the second solvent respectively and then contacting them under hypergravity conditions can avoid local pH changes caused by the local reaction of oxidant in the remediation agent, thereby avoiding the deactivation of oxidant. Therefore, a small amount of oxidant can be used to achieve a high organic pollutant degradation efficiency. Detailed Implementation

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] The first aspect of this invention provides a method for remediating contaminated soil, the method comprising:

[0021] (1) The contaminated soil is mixed with a first solvent to obtain a first mixture;

[0022] (2) The repair agent is mixed with the second solvent to obtain a second mixture;

[0023] (3) The first mixture and the second mixture are brought into contact under hypergravity conditions.

[0024] In some embodiments of the present invention, the dosage of the remediation agent is 0.1-50 g / kg of contaminated soil, for example, it can be any one of the following values, or a value within the range of any two of the above: 0.1 g / kg contaminated soil, 0.5 g / kg contaminated soil, 1 g / kg contaminated soil, 2 g / kg contaminated soil, 3 g / kg contaminated soil, 4 g / kg contaminated soil, 5 g / kg contaminated soil, 6 g / kg contaminated soil, 7 g / kg contaminated soil, 8 g / kg contaminated soil, 9 g / kg contaminated soil, 10 g / kg contaminated soil, 15 g / kg contaminated soil, 20 g / kg contaminated soil, 25 g / kg contaminated soil, 30 g / kg contaminated soil, 35 g / kg contaminated soil, 40 g / kg contaminated soil, 45 g / kg contaminated soil, and 50 g / kg contaminated soil. Preferably, the dosage of the remediation agent is 0.5-16 g / kg contaminated soil.

[0025] In some embodiments of the present invention, the amount of the first solvent used is 1-5 L relative to 1 kg of contaminated soil.

[0026] In some embodiments of the present invention, the amount of the second solvent used is 5-500 mL relative to 1 g of repair agent. Preferably, the amount of the second solvent used is 7-200 mL relative to 1 g of repair agent.

[0027] In some embodiments of the present invention, the remedial agent contains an oxidant, an optional catalyst, an optional chelating agent, and an optional initiator.

[0028] In some embodiments of the present invention, the repair agent does not contain surfactants or solubilizers.

[0029] In some embodiments of the present invention, the amount of oxidant used is 0.1-50 g / kg of contaminated soil, for example, it can be any one of the following values, or a value within a range of any two of the following: 0.1 g / kg contaminated soil, 0.5 g / kg contaminated soil, 1 g / kg contaminated soil, 2 g / kg contaminated soil, 3 g / kg contaminated soil, 4 g / kg contaminated soil, 5 g / kg contaminated soil, 6 g / kg contaminated soil, 7 g / kg contaminated soil, 8 g / kg contaminated soil, 9 g / kg contaminated soil, 10 g / kg contaminated soil, 15 g / kg contaminated soil, 20 g / kg contaminated soil, 25 g / kg contaminated soil, 30 g / kg contaminated soil, 35 g / kg contaminated soil, 40 g / kg contaminated soil, 45 g / kg contaminated soil, and 50 g / kg contaminated soil. Preferably, the amount of oxidant used is 0.5-9 g / kg contaminated soil. The inventors have found that when the amount of oxidant is within the preferred range, the removal rate of organic pollutants can be further improved under hypergravity conditions.

[0030] In some embodiments of the present invention, the catalyst is a ferrous salt and / or a bisulfite. Preferably, the ferrous salt is at least one selected from ferrous sulfate, ferrous chloride, ferrous oxide, and ferrous carbonate, and the bisulfite is at least one selected from sodium bisulfite, potassium bisulfite, ammonium bisulfite, and calcium bisulfite.

[0031] In some embodiments of the present invention, the content of the catalyst is 60-500 parts by weight relative to 100 parts by weight of the oxidant, for example, it can be any one of 60 parts by weight, 70 parts by weight, 80 parts by weight, 90 parts by weight, 100 parts by weight, 120 parts by weight, 140 parts by weight, 160 parts by weight, 180 parts by weight, 200 parts by weight, 250 parts by weight, 300 parts by weight, 350 parts by weight, 400 parts by weight, 450 parts by weight, or 500 parts by weight, or a value within a range of any two of the above values.

[0032] In some embodiments of the present invention, the oxidant contains at least one of peroxide, persulfate, permanganate and percarbonate.

[0033] In some embodiments of the present invention, the peroxide is at least one of calcium peroxide, potassium peroxide, and magnesium peroxide.

[0034] In some embodiments of the present invention, the persulfate is at least one of sodium persulfate, potassium persulfate, and ammonium persulfate.

[0035] In some embodiments of the present invention, the permanganate is at least one of potassium permanganate, magnesium permanganate, and zinc permanganate.

[0036] In some embodiments of the present invention, the percarbonate is sodium percarbonate and / or calcium percarbonate.

[0037] In some embodiments of the present invention, the oxidant is a composition of peroxide and persulfate. The inventors discovered that when the oxidant is a composition of peroxide and persulfate, under hypergravity conditions, the peroxide can generate highly reactive hydroxyl radicals, which not only more effectively degrade organic pollutants but also further promote the activation of persulfate, while only a small amount of peroxide decomposes to generate oxygen. Therefore, when the oxidant contains both peroxide and persulfate, the oxidant can achieve better pollutant degradation with a smaller dosage. Preferably, the mass ratio of the peroxide to persulfate is 1:1-10, more preferably 1:3-6.

[0038] In some embodiments of the present invention, the amount of the initiator is 1-4 parts by weight relative to 1000 parts by weight of the oxidant.

[0039] In some embodiments of the present invention, the initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azobisisobutylammonoacetic acid, and azobisisopropylimidazoline.

[0040] In some preferred embodiments of the present invention, the remediation agent contains an oxidant and an initiator. When the remediation agent contains the aforementioned components, it exhibits comparable or better organic pollutant degradation effects compared to remediation agents containing oxidants, catalysts, and / or chelating agents, resulting in a higher organic pollutant degradation rate when used for soil remediation. Therefore, when the remediation agent contains the aforementioned components, the use of catalysts and chelating agents can be avoided, thereby preventing the catalysts and chelating agents from affecting the soil structure after remediation, reducing remediation costs. Furthermore, the decomposition products of the initiator are non-toxic, further preventing secondary pollution. Preferably, the amount of the initiator is 1-4 parts by weight relative to 1000 parts by weight of the oxidant. More preferably, the initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azodicyanovalerate, and azobisisopropylimidazoline. More preferably, when the oxidant is a peroxide and a persulfate, the peroxide and persulfate have a synergistic effect, further improving the degradation effect of organic pollutants. In a preferred embodiment, the mass ratio of the peroxide to the persulfate is 1:1-10, and more preferably 1:3-6.

[0041] In some embodiments of the present invention, the amount of the chelating agent is 50-300 parts by weight relative to 100 parts by weight of the oxidant.

[0042] In some embodiments of the present invention, the chelating agent is at least one of citric acid, EDTA, and tartaric acid.

[0043] In some embodiments of the present invention, the first solvent and the second solvent are each independently selected from at least one of water and an aqueous ethanol solution. Preferably, the first solvent and the second solvent are water.

[0044] In some embodiments of the present invention, the volume ratio of ethanol to water in the aqueous ethanol solution is 1:1-20.

[0045] In some embodiments of the present invention, the pollutants in the contaminated soil are organic pollutants, preferably at least one of petroleum hydrocarbons, benzene compounds, and polycyclic aromatic hydrocarbons.

[0046] In this invention, the petroleum hydrocarbon refers to at least one of alkanes and alkenes having 10-40 carbon atoms, or a mixture of alkanes and alkenes having 10-40 carbon atoms.

[0047] In some embodiments of the present invention, step (3) is performed in a hypergravity machine, and step (3) includes feeding the first mixture and the second mixture into the hypergravity machine before contact.

[0048] In some embodiments of the present invention, the feed temperature of the first mixture is 20-40°C. When the feed temperature of the first mixture is within the above range, the increased repair costs caused by heating the material can be avoided.

[0049] In some embodiments of the present invention, the feed temperature of the second mixture is 20-65°C.

[0050] When the remediation agent contains an initiator, the feed temperature of the second mixture is 50-65°C. When the feed temperature of the second mixture is within this range, the initiator can be activated, thereby activating the oxidant to generate free radicals, further improving the degradation rate of organic pollutants.

[0051] In some embodiments of the present invention, the feed rate of the first mixture is controlled such that the feed time of the first mixture is 0.1-20 min.

[0052] In some embodiments of the present invention, the feed rate of the second mixture is 0.05-0.5 times that of the feed rate of the first mixture.

[0053] In some embodiments of the present invention, the feed rate of the first mixture is constant, and the feed rate of the second mixture is constant.

[0054] When the feed rates of the first mixture and the second mixture are within the above range, the contaminated soil and the remediation agent can be fully mixed and contacted, improving the dispersibility of the remediation agent in the contaminated soil, maximizing the role of the oxidant in the remediation agent, and reducing the amount of remediation agent used.

[0055] In some embodiments of the present invention, the hypergravity conditions are: a rotation speed of 400-4000 rpm. When the rotation speed exceeds 4000 rpm, the required energy consumption is high; when the rotation speed is below 400 rpm, the first mixture and the second mixture cannot be mixed evenly in the hypergravity machine, resulting in insufficient contact between the remediation agent and the contaminated soil. Preferably, the rotation speed is 2000-3000 rpm. When the rotation speed is within the preferred range, the two mixtures can be mixed evenly in the hypergravity machine, and the remediation agent can make sufficient contact with the contaminated soil, thereby improving the remediation effect.

[0056] In some embodiments of the present invention, the contact time is 1-60 minutes. When the contact time is less than 1 minute, the remediation agent cannot fully exert its function, resulting in poor remediation effect; when the contact time exceeds 60 minutes, the activity of the oxidant in the remediation agent has significantly decreased, and increasing the contact time does not significantly promote the degradation of pollutants, but instead increases the remediation cost. Preferably, the contact time is 5-20 minutes. When the contact time is within the preferred range, the remediation agent can exert its function to the maximum extent with the lowest energy consumption, achieving the best remediation effect.

[0057] In some embodiments of the present invention, the method further includes: performing solid-liquid separation on the material after contact in step (3), and the resulting solid phase is the remediated soil.

[0058] In this invention, the solid-liquid separation can be performed using conventional techniques in the field, such as centrifugation.

[0059] A second aspect of the present invention provides the application of the method described above in reducing the content of organic pollutants in organically contaminated soil.

[0060] In some embodiments of the present invention, the organic pollutant is at least one of petroleum hydrocarbons, benzene compounds, and polycyclic aromatic hydrocarbons.

[0061] The present invention will be described in detail below through embodiments.

[0062] In the following examples, unless otherwise specified, all reagents used are commercially available, and all methods used are conventional methods in the art.

[0063] In the following examples, the contaminated soil samples were prepared according to the following method:

[0064] (a) Collect soil from the 0-20cm topsoil layer, remove gravel and plant and animal remains from the soil, dry it at 200℃ and then pass it through a 2mm sieve for later use.

[0065] (b) Dissolve a certain amount of organic pollutants in dichloromethane. While continuously stirring, add the prepared organic pollutant / dichloromethane solution to the uncontaminated soil from step (a) above. Continue stirring until homogeneous, then place in a fume hood to allow the solvent to evaporate naturally, thus obtaining organically contaminated soil. Depending on the amount of organic pollutants added, contaminated soil with different organic pollutant contents can be prepared. The prepared contaminated soil must contain at least one organic pollutant with a content exceeding the risk screening value for Class II construction land soil pollution as specified in the "Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control (Trial)" (GB 36600-2018).

[0066] In the following examples, the content of petroleum hydrocarbons is in accordance with the "Petroleum Hydrocarbons in Soil and Sediments (C)" standard. 10 -C 40 The determination of ) by gas chromatography (HJ 1021-2019) is required.

[0067] The naphthalene content was determined according to the "Determination of Polycyclic Aromatic Hydrocarbons in Soil and Sediments by High Performance Liquid Chromatography" (HJ784-2016).

[0068] In the following embodiments, unless otherwise specified, the feed temperature of the first mixture and the second mixture is 25°C.

[0069] Example 1

[0070] (1) Use petroleum hydrocarbons (C) that meet the requirements of HJ 1021-2019. 10 -C 40 The standard solution was used to prepare petroleum hydrocarbon contaminated soil as an organic pollutant. The petroleum hydrocarbon content in the contaminated soil was found to be 10,000 mg / kg, which significantly exceeded the requirement of 4,500 mg / kg for petroleum hydrocarbon soil pollution risk screening value for Class II construction land in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)".

[0071] (2) Weigh 1000g of the contaminated soil obtained in step (1) and place it in a beaker. Add 3000mL of deionized water and stir continuously to mix the contaminated soil and water evenly to obtain the first mixture.

[0072] (3) Add 1g of calcium peroxide and 3.861g of ferrous sulfate to 300mL of deionized water and mix well to obtain the second mixture.

[0073] (4) Turn on the centrifuge and adjust the speed to 2500 rpm. After it stabilizes, add the first mixture and the second mixture to the centrifuge at feed rates of 300 mL / min and 30 mL / min, respectively. After feeding, react for 10 min, and then discharge the reactants from the centrifuge outlet.

[0074] (5) The reactants obtained in step (4) are centrifuged to separate the aqueous phase and the soil phase. The aqueous phase is discarded, and the soil phase is the remediated soil. The remediated soil contains organic pollutants (i.e., petroleum hydrocarbons (C)). 10 -C 40 The content of )) was tested.

[0075] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0076] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0077] Example 2

[0078] The contaminated soil was remediated in the same manner as in Example 1, except that step (3) was: 1g of sodium persulfate and 1.169g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0079] The content of organic pollutants and degradation rates in the remediated soil are shown in Table 1.

[0080] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0081] Example 3

[0082] The contaminated soil was remediated using the same method as in Example 1, except that step (3) was performed as follows: 1 g of potassium permanganate and 0.656 g of sodium bisulfite were added to 300 mL of deionized water and mixed evenly to obtain a second mixture.

[0083] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0084] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0085] Example 4

[0086] The contaminated soil was remediated in the same manner as in Example 1, except that step (3) was: 1g of sodium percarbonate and 0.885g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0087] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0088] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0089] Example 5

[0090] The contaminated soil was remediated using the same method as in Example 1, except that step (3) was performed as follows: 1g of calcium peroxide, 3.309g of sodium persulfate and 3.861g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0091] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0092] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0093] Example 6

[0094] The contaminated soil was remediated using the same method as in Example 1, except that step (1) was as follows: Naphthalene-contaminated soil was prepared using naphthalene as an organic pollutant, and the naphthalene content in the contaminated soil was tested to be 300 mg / kg, which significantly exceeded the requirement of the second-class construction land naphthalene soil pollution risk screening value (70 mg / kg) in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)".

[0095] The content and degradation rate of organic pollutants (i.e. naphthalene) in the remediated soil are shown in Table 1.

[0096] Degradation rate = [(Naphthalene content in contaminated soil - Naphthalene content in remediated soil) / Naphthalene content in contaminated soil] × 100%.

[0097] Example 7

[0098] The contaminated soil was remediated using the same method as in Example 1, except that step (3) was performed as follows: 2g of calcium peroxide and 7.72g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0099] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0100] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0101] Example 8

[0102] The contaminated soil was remediated in the same manner as in Example 1, except that step (2) was as follows: 1000g of the contaminated soil obtained in step (1) was weighed and placed in a beaker, 1000mL of deionized water was added, and the mixture was stirred continuously to make the contaminated soil and water evenly mixed to obtain the first mixture; step (3) was as follows: 1g of calcium peroxide and 3.861g of ferrous sulfate were added to 100mL of deionized water and mixed evenly to obtain the second mixture.

[0103] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0104] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0105] Example 9

[0106] The contaminated soil remediation was carried out using the same method as in Example 1, except that step (4) was as follows: the centrifuge was turned on, the speed was adjusted to 3000 rpm, and after it was running stably, the first mixture and the second mixture were simultaneously added to the centrifuge at feed rates of 300 mL / min and 30 mL / min, respectively. After the feed was completed, the reaction was allowed to proceed for 10 min, and then the reactants were discharged from the outlet of the centrifuge.

[0107] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0108] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0109] Example 10

[0110] The contaminated soil remediation was carried out using the same method as in Example 1, except that step (3) was as follows: the centrifuge was turned on, the rotation speed was adjusted to 2500 rpm, and after it was running stably, the first mixture and the second mixture were simultaneously added to the centrifuge at feed rates of 800 mL / min and 80 mL / min, respectively. After the feed was completed, the reaction was allowed to proceed for 10 min, and then the reactants were discharged from the outlet of the centrifuge.

[0111] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0112] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0113] Example 11

[0114] The contaminated soil remediation was carried out using the same method as in Example 1, except that step (3) was as follows: the centrifuge was turned on, the rotation speed was adjusted to 2500 rpm, and after it was running stably, the first mixture and the second mixture were simultaneously added to the centrifuge at feed rates of 300 mL / min and 30 mL / min, respectively. After the feed was completed, the reaction was carried out for 20 min, and then the reactants were discharged from the outlet of the centrifuge.

[0115] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0116] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0117] Example 12

[0118] The contaminated soil was remediated using the same method as in Example 5, except that step (3) was as follows: 1g of calcium peroxide, 5g of sodium persulfate and 4.851g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0119] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0120] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0121] Example 13

[0122] The contaminated soil was remediated using the same method as in Example 5, except that step (3) was performed as follows: 1g of calcium peroxide, 8g of sodium persulfate and 6.603g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0123] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0124] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0125] Example 14

[0126] The contaminated soil remediation was carried out using the same method as in Example 5, except that step (4) involved turning on the centrifuge, adjusting the speed to 2500 rpm, and after it stabilized, simultaneously adding the first and second mixtures to the centrifuge at feed rates of 300 mL / min and 30 mL / min, respectively. After feeding, the reaction was allowed to proceed for 60 minutes, and then the reactants were discharged from the centrifuge outlet.

[0127] The content of organic pollutants in the remediated soil is shown in Table 1.

[0128] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0129] Example 15

[0130] The contaminated soil was remediated using the same method as in Example 5, except that step (3) was performed as follows: 5g of calcium peroxide, 16.55g of sodium persulfate and 19.4g of ferrous sulfate were added to 300mL of deionized water and mixed evenly to obtain a second mixture.

[0131] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0132] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0133] Example 16

[0134] The contaminated soil remediation was carried out using the same method as in Example 5, except that step (3) was performed as follows: 1 g of calcium peroxide, 3.309 g of sodium persulfate, and 0.008 g of azobisisobutylamidine hydrochloride were added to 300 mL of deionized water, heated to 50 °C, and mixed evenly to obtain a second mixture. In step (4), the feed temperature of the second mixture was 50 °C.

[0135] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0136] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0137] Example 17

[0138] The contaminated soil remediation was carried out using the same method as in Example 5, except that step (3) was performed as follows: 1g of calcium peroxide, 5g of sodium persulfate, and 0.012g of azobisisobutylamidine hydrochloride were added to 300mL of deionized water, heated to 50°C, and mixed thoroughly to obtain a second mixture. In step (4), the feed temperature of the second mixture was 50°C.

[0139] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0140] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0141] Example 18

[0142] The contaminated soil remediation was carried out using the same method as in Example 5, except that step (3) was as follows: 1g of calcium peroxide, 3.309g of sodium persulfate, and 0.008g of azobisisobutyrazoline hydrochloride were added to 300mL of deionized water, heated to 50°C, and mixed thoroughly to obtain a second mixture. In step (4), the feed temperature of the second mixture was 50°C.

[0143] The content of organic pollutants in the remediated soil is shown in Table 1.

[0144] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0145] Comparative Example 1

[0146] The contaminated soil was remediated in the same manner as in Example 1, except that step (4) was as follows: the first mixture and the second mixture were mixed at feed rates of 300 mL / min and 30 mL / min respectively under continuous stirring, and the reaction was carried out for 10 min after the feed was completed.

[0147] The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0148] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0149] Comparative Example 2

[0150] Petroleum hydrocarbon-contaminated soil with a concentration of 10000 mg / kg was prepared. 1000 g of petroleum hydrocarbon-contaminated soil, 1 g of calcium peroxide, and 3.861 g of ferrous sulfate were weighed and added to 3300 mL of deionized water. The mixture was stirred continuously until homogeneous. A centrifuge was turned on and the speed was adjusted to 2500 rpm. After stable operation, the mixture was added to the centrifuge at a feed rate of 330 mL / min. After feeding, the reaction was allowed to proceed for 10 minutes, and then the reactants were discharged from the centrifuge outlet. The reactants were centrifuged to separate the aqueous and soil phases. The aqueous phase was discarded, and the soil phase was the remediated soil. The remediated soil was then treated to remove organic pollutants (i.e., petroleum hydrocarbons (C...). 10 -C 40 The content of organic pollutants in the remediated soil was tested. The content and degradation rate of organic pollutants in the remediated soil are shown in Table 1.

[0151] Degradation rate = [(Petroleum hydrocarbon content in contaminated soil - Petroleum hydrocarbon content in remediated soil) / Petroleum hydrocarbon content in contaminated soil] × 100%.

[0152] Table 1

[0153]

[0154]

[0155] The results above demonstrate that the method of this invention, utilizing a supergravity mixing process, can improve soil remediation efficiency, shorten remediation time, and reduce remediation costs, without causing secondary soil pollution. This method is applicable to various remediation agent systems, achieving a degradation rate of over 80% for various organic pollutants in the soil, and preferably over 90%. The organic pollutant content in the remediated soil is lower than the risk screening value for Class II construction land soil pollution specified in the "Soil Environmental Quality Standard for Construction Land Soil Pollution Risk Control (Trial Implementation)," indicating promising application prospects.

[0156] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for remediating contaminated soil, characterized in that, The method includes: (1) The contaminated soil is mixed with the first solvent to obtain a first mixture; (2) The repair agent is mixed with the second solvent to obtain a second mixture; (3) The first mixture and the second mixture are brought into contact under hypergravity conditions for a contact time of 5-20 min; The dosage of the remediation agent is 0.1-50 g / kg of contaminated soil; The repair agent does not contain surfactants or solubilizers; The repair agent contains an oxidant and an initiator; The oxidant is a composition of peroxide and persulfate, wherein the mass ratio of the peroxide to the persulfate is 1:1-10; The amount of the initiator is 1-4 parts by weight relative to 1000 parts by weight of the oxidant; The first solvent and the second solvent are each independently selected from at least one of water and aqueous ethanol solution; The pollutants in the contaminated soil are organic pollutants.

2. The method according to claim 1, wherein, The dosage of the remediation agent is 0.5-16 g / kg of contaminated soil; And / or, relative to 1 kg of contaminated soil, the amount of the first solvent used is 1-5 L; And / or, relative to 1g of repair agent, the amount of the second solvent is 5-500mL.

3. The method according to claim 1, wherein, The oxidant is a composition of peroxide and persulfate, wherein the mass ratio of the peroxide to the persulfate is 1:3-6; And / or, the initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azobisisobutylammonoacetic acid, and azobisisopropylimidazoline.

4. The method according to claim 1, wherein, The first solvent and the second solvent are water.

5. The method according to claim 1, wherein, The pollutants in the contaminated soil are at least one of petroleum hydrocarbons, benzene compounds, and polycyclic aromatic hydrocarbons.

6. The method according to any one of claims 1-4, wherein, Step (3) is carried out in a hypergravity machine, which includes feeding the first mixture and the second mixture into the hypergravity machine before contact.

7. The method according to claim 6, wherein, When the second mixture contains an oxidant and an initiator, the feed temperature of the second mixture is 20-65°C; And / or, control the feed rate of the first mixture so that the feed time of the first mixture is 0.1-20 min; And / or, the feed rate of the second mixture is 0.05-0.5 times the feed rate of the first mixture.

8. The method according to any one of claims 1-4, wherein, The condition for the hypergravity is: a rotational speed of 400-4000 rpm.

9. The method according to claim 8, wherein, The condition for the hypergravity is: a rotational speed of 2000-3000 rpm.

10. The method according to any one of claims 1-4, wherein, The method further includes: performing solid-liquid separation on the material after contact in step (3), and the resulting solid phase is the remediated soil.

11. The application of the method according to any one of claims 1-10 in reducing the content of organic pollutants in organic-contaminated soil.

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