A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation

Abstract

The present application relates to the field of soil remediation, and more specifically, it relates to a method for enhanced chemical oxidation treatment of semi-volatile organic polluted soil. A method for enhanced chemical oxidation treatment of semi-volatile organic polluted soil, comprising the following steps: screening: screening the soil to be treated for large particles to remove large impurities; scrubbing: adding a treatment agent to mix with the soil to be treated to form a mixture; the treatment agent and the soil to be treated are used in a ratio of 1:100 by weight; the treatment agent includes modified biochar and persulfate; the modified biochar includes sludge, waste rice bran, ferric oxide, cobalt oxide, nickel oxide, and water by weight; primary vibration and secondary vibration; magnetic separation of the screened material of the secondary vibration to recover the modified biochar; and discharge of the soil to be tested after passing the test. The present application has the advantage of further removing semi-volatile organic matter in the soil.

Description

Technical Field

[0001] The present application relates to the field of soil remediation, and more specifically, to a method for treating semi-volatile organic polluted soil by enhanced chemical oxidation. Background Art

[0002] Soil refers to the loose surface layer of the land that is fertile and can grow plants. It can provide conditions and nutrients for plant growth and development. Soil is the basic material guarantee for the survival and reproduction of many organisms and is an important resource for people to survive.

[0003] However, with the development of urbanization and industrialization, more and more soils are polluted. For example, solid waste is piled up and dumped on the soil surface, polluted wastewater penetrates into the soil, and harmful gases and dust in the atmosphere fall into the soil with rainwater. These are all ways of soil pollution. The normal functions of the soil are reduced or lost, and it may even indirectly affect human health through the crops grown.

[0004] Semi-volatile organic compounds are one of the main soil pollutants in decommissioned industrial sites. They are widely distributed in the soil, are toxic and bioaccumulative, and will continuously migrate in environmental media such as soil, water, and atmosphere through processes such as leaching, volatilization, and sedimentation, and eventually accumulate in the soil. Common semi-volatile organic compounds include phenols, anilines, nitroaromatic hydrocarbons, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls.

[0005] At present, the methods for removing semi-volatile organic compounds from soil mainly include soil leaching (elution process), chemical oxidation process, etc. Among them, soil leaching (elution process) mainly increases the solubility of organic matter in water by adding surfactants, and promotes the transfer of organic matter from the solid phase to the liquid phase, so as to achieve the purpose of soil purification and treatment. However, due to the relatively low solubility of semi-volatile organic matter in water, even if excessive surfactants are added, a large amount of semi-volatile organic pollutants still remain in the fine particles of soil, and the efficiency and effect of soil remediation are low. Therefore, there is still room for improvement.

[0006] The chemical oxidation process mainly involves adding persulfate, Fenton and other oxidants and corresponding catalysts to remove organic pollutants by chemical oxidation on the surface of soil particles. A large amount of catalysts needs to be added, and most of the catalysts cannot be recycled and reused, which not only causes waste, but also the additional addition of a large amount of chemicals will lead to problems such as soil compaction and salinization. Therefore, there is still room for improvement. Summary of the invention

[0007] In order to further remove semi-volatile organic compounds in soil, the present application provides a method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation.

[0008] The present application provides a method for treating semi-volatile organic polluted soil by enhanced chemical oxidation, which adopts the following technical scheme:

[0009] A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation comprises the following steps:

[0010] Screening: Screen the soil to be treated into large particles to remove large impurities;

[0011] Scrubbing: adding a treatment agent and mixing it with the soil to be treated to form a mixture; the ratio of the treatment agent to the soil to be treated is 1:100 by weight; the treatment agent includes the following raw materials by weight: 100-120 parts of modified biochar, 55-80 parts of persulfate; the modified biochar includes the following preparation raw materials by weight: 65-85 parts of sludge, 15-35 parts of waste rice bran, 5-10 parts of ferric oxide, 8-15 parts of cobalt oxide, 2-7 parts of nickel oxide, and 50-70 parts of water;

[0012] Primary vibration, secondary vibration;

[0013] The undersize material of the secondary vibration is subjected to magnetic separation to recover the modified biochar;

[0014] After the soil is tested and found to be qualified, it will be discharged.

[0015] By adopting the above technical solution, a treatment agent is added during the scrubbing process to treat semi-volatile organic matter. Under the catalysis of modified biochar, the persulfate in the treatment agent directly contacts the fine particles in the soil, and an oxidation reaction occurs between the persulfate and the fine particles, thereby separating the organic pollutants adsorbed in the fine particles of the soil, especially the semi-volatile organic pollutants, from the fine particles of the soil, thereby achieving soil purification.

[0016] During the preparation of modified biochar, the specific ratio of ferric oxide, cobalt oxide, nickel oxide, sludge and waste rice bran can further promote the stable breaking of more carbon-oxygen bonds and carbon-carbon bonds, thereby generating more persistent free radicals. At the same time, the quinone and phenolic groups generated by the anaerobic pyrolysis process can also form a certain amount of persistent free radicals on the surface of the modified biochar after electron transfer.

[0017] In addition, calcination is required when preparing modified biochar. During this process, biomass is pyrolyzed at high temperature and without oxygen. 3It will be regulated and transformed, thus destroying the carbon skeleton. However, the destruction is not completely negative. Due to the destruction, there are some structural defects on the carbon skeleton. These structural defects cooperate with ferric oxide, cobalt oxide, and nickel oxide to increase the overall active sites of the modified biochar and improve the catalytic ability. This can further improve the adsorption of persulfate, so that persulfate has a close and firm contact with the surface of soil fine particles, the oxidation reaction is more thorough, and the degradation effect of semi-volatile organic matter in the soil is further improved.

[0018] The use of ferrosoferric oxide and cobalt oxide not only changes the structure of the modified biochar, but also gives the modified biochar good magnetic properties.

[0019] The special modified biochar and persulfate are added to the soil to be treated in a specific ratio, which has a relatively suitable persistent free radical concentration and can promote the oxidation of semi-volatile organic matter by persulfate. At the same time, because the modified biochar is magnetic, it can be easily separated from the soil for recycling, reducing the use of chemicals and the cost of soil remediation; and the treated soil contains almost no modified biochar, and the subsequent planting of crops will not be affected.

[0020] Preferably, the weight ratio of the sludge to the waste rice bran is (70-80):(20-30).

[0021] By adopting the above technical solution, sludge and waste rice bran are used in a specific ratio, which is beneficial to provide more active sites for catalyzing persulfate.

[0022] Moreover, when municipal sludge is used, a large amount of polyferric chloride will be added during the sludge dehydration process. This part of the iron element will also be solidified when preparing the modified biochar, which is beneficial to further enhance the magnetic properties of the modified biochar.

[0023] Preferably, the weight ratio of cobalt oxide to nickel oxide is (10-12): (2-4).

[0024] By adopting the above technical solution, the usage ratio of cobalt tetroxide and nickel oxide is further limited, which is beneficial to increase the speed of electron transfer, shorten the time for forming persistent free radicals on the surface of modified biochar, and also help shorten the preparation time of the entire modification.

[0025] Preferably, the treatment agent also includes 200-300 parts of activated carbon.

[0026] By adopting the above technical solution, a certain amount of activated carbon is added to the treatment agent. When the treatment agent comes into contact with the soil, the activated carbon reacts with volatile organic matter first, and adsorbs the volatile organic matter into the structure; so that persulfate and modified biochar can react with semi-volatile organic matter more preferentially; it is beneficial to improve the overall purification effect of the treatment agent on the treated soil.

[0027] Preferably, the method for preparing the modified biochar comprises the following steps:

[0028] Mixing ferroferric oxide, cobalt trioxide, nickel oxide and water, and stirring at 1000-1200 r / min until uniform, to obtain a solution for use;

[0029] The liquid to be used is mixed with the sludge and the waste rice bran at 600-800 r / min until uniform, and then allowed to stand for 2-8 hours;

[0030] Then dry at 50-80°C for 6-12h to obtain a semi-finished product;

[0031] The semi-finished product is calcined at 350-500° C. under anaerobic conditions for 60-120 min to obtain modified biochar.

[0032] Since the modified biochar prepared in this application is not used to adsorb and remove harmful substances in the soil, but mainly plays the role of catalyzing the reaction between persulfate and soil, a specific calcination temperature and calcination time are used to prepare the modified biochar, so that the surface of the modified biochar has abundant functional groups, and a large number of oxygen-containing functional groups are also retained, which is beneficial to serve as a catalytic site or an intermediate for electron transfer to improve the overall catalytic effect of the modified biochar on persulfate.

[0033] Preferably, when the semi-finished product is calcined, it is transferred to a nitrogen protective atmosphere with a heating rate of 10-12°C / min until it is heated to 350-500°C.

[0034] By adopting the above technical solution, the heating rate is further limited, excess impurities are removed, the modification preparation is carried out stably, and modified biochar with a stable structure is generated.

[0035] Preferably, the particle size of the ferrosoferric oxide is 20-50 μm.

[0036] During the soil remediation process, nano-scale raw materials are difficult to disperse evenly and are prone to agglomeration.

[0037] By adopting the above technical solution, the particle size of the modified biochar is further limited to the micrometer level. After actual testing, the specially selected ferroferric oxide in the present application is involved in the preparation of the modified biochar, which can have a good dispersion effect and enable the modified biochar to play a good catalytic effect.

[0038] Preferably, during the scrubbing, the solid-liquid ratio of the soil to be treated and water is 1:(1.2-1.5).

[0039] By adopting the above technical solution, certain liquid phase conditions are provided for the oxidation of persulfate, which is conducive to achieving better mass transfer effect, and the treatment agent can have a better dispersion effect at this concentration.

[0040] Preferably, the method for preparing the treating agent comprises the following steps: mixing the raw materials and stirring until they are uniform.

[0041] The preparation method of the treatment agent provided in the present application is simple and convenient, and because the treatment agent contains magnetic modified biochar, it can be reused through magnetic recovery, which is beneficial to reduce costs and is more suitable for promotion and use in this field.

[0042] In summary, this application has the following beneficial effects:

[0043] 1. During the scrubbing process, add a treatment agent to treat semi-volatile organic matter. Under the catalysis of modified biochar, the persulfate in the treatment agent directly contacts the fine particles in the soil, and an oxidation reaction occurs between the fine particles of the soil, thereby separating the organic pollutants adsorbed in the fine particles of the soil, especially the semi-volatile organic pollutants, from the fine particles of the soil, thereby achieving soil purification.

[0044] 2. The specific ratio of ferric oxide, cobalt oxide, nickel oxide, sludge and waste rice bran can further promote the stable breaking of more carbon-oxygen bonds and carbon-carbon bonds, thereby generating more persistent free radicals. At the same time, the quinone and phenolic groups generated by the anaerobic pyrolysis process can also form a certain amount of persistent free radicals on the surface of the modified biochar after electron transfer.

[0045] 3. Structural defects cooperate with ferric oxide, cobalt oxide, and nickel oxide to increase the overall active sites of modified biochar and improve catalytic capacity. This can further improve the adsorption of persulfate, so that persulfate has a close and firm contact with the surface of soil fine particles, the oxidation reaction is more thorough, and the degradation effect of semi-volatile organic matter in the soil is further improved.

[0046] 4. Due to the use of ferroferric oxide and cobalt oxide, the structure of the modified biochar is changed and the modified biochar is endowed with good magnetic properties. The modified biochar can be easily separated from the soil for recycling, reducing the use of chemicals and the cost of soil remediation. The treated soil contains almost no modified biochar, and subsequent crop planting will not be affected. DETAILED DESCRIPTION

[0047] The present application is further described in detail below with reference to the embodiments.

[0048] The raw materials used in the following examples and comparative examples are all commercially available products.

[0049] Preparation Example

[0050] Preparation Example 1

[0051] A modified biochar comprises the following preparation raw materials: 70 kg of sludge, 30 kg of waste rice bran, 6 kg of ferrosoferric oxide, 10 kg of cobalt oxide, 4 kg of nickel oxide, and 60 kg of water.

[0052] Among them, the sludge is municipal sludge.

[0053] The particle size of ferrosoferric oxide is 20 μm.

[0054] A method for preparing modified biochar comprises the following steps:

[0055] Step 1): Pour water into a stirring pot, then add ferroferric oxide, cobalt oxide and nickel oxide into the stirring pot in sequence, and stir at 1000 r / min for 25 minutes to obtain a standby solution.

[0056] Step 2): Put the sludge and the waste rice bran into the reaction pot together and stir until they are uniform. Then put the standby liquid into the reaction pot and mix it with the sludge and the waste rice bran, mix them at 800r / min until they are uniform, and let it stand for 5 hours.

[0057] Step 3): Dry the material after standing in step 2) at 80° C. for 6 hours to obtain a semi-finished product.

[0058] Step 4): The semi-finished product was transferred to a nitrogen protective atmosphere, placed in a muffle furnace, and the heating rate was controlled to be 10° C. / min until the temperature rose to 400° C., and calcined at this temperature for 90 min to obtain a crude product.

[0059] Step 5): The crude product is washed with water, filtered, and vacuum dried to obtain modified biochar.

[0060] Preparation Example 2

[0061] A modified biochar, which is different from Preparation Example 1 in that:

[0062] The weight ratio of sludge to waste rice bran is 80:20, that is, 80 kg of sludge and 20 kg of waste rice bran.

[0063] The weight ratio of cobalt tetroxide to nickel oxide is 12:2, that is, cobalt tetroxide is 12 kg and nickel oxide is 2 kg.

[0064] Preparation Example 3

[0065] A modified biochar, which is different from Preparation Example 1 in that the weight ratio of sludge to waste rice bran is 65:35, that is, the sludge is 65 kg and the waste rice bran is 35 kg.

[0066] Preparation Example 4

[0067] A modified biochar is different from Preparation Example 1 in that the weight ratio of cobalt tetroxide to nickel oxide is 8:6, that is, cobalt tetroxide is 8 kg and nickel oxide is 6 kg.

[0068] Preparation Example 5

[0069] A method for preparing modified biochar, which is different from Preparation Example 1 in that in step 4), the semi-finished product is calcined at 650° C. for 90 minutes to obtain a crude product.

[0070] Preparation Example 6

[0071] A method for preparing modified biochar is different from Preparation Example 1 in that the drying operation of step 3) is omitted.

[0072] Preparation Example 7

[0073] A method for preparing modified biochar, which is different from Preparation Example 1 in that in step 2), mixing is performed at 100 r / min until uniform.

[0074] Preparation Example 8

[0075] A modified biochar, which is different from Preparation Example 1 in that the particle size of ferrosoferric oxide is 10 nm.

[0076] Preparation Example 9

[0077] A modified biochar, which is different from Preparation Example 1 in that it includes the following preparation raw materials: 65kg sludge, 35kg waste rice bran, 10kg ferrosoferric oxide, 8kg cobalt oxide, 7kg nickel oxide, and 70kg water.

[0078] The particle size of ferrosoferric oxide is 50 μm.

[0079] A method for preparing modified biochar, which is different from Preparation Example 1 in that:

[0080] Step 2) was allowed to stand for 2 hours;

[0081] In step 3), drying at 50° C. for 12 h;

[0082] In step 4), the heating rate is 12°C / min, the temperature rises to 350°C, and the calcination treatment is performed for 120 minutes.

[0083] Preparation Example 10

[0084] A modified biochar, which is different from Preparation Example 1 in that it includes the following preparation raw materials: 85kg sludge, 15kg waste rice bran, 5kg ferrosoferric oxide, 15kg cobalt oxide, 2kg nickel oxide, and 50kg water.

[0085] A method for preparing modified biochar, which is different from Preparation Example 1 in that:

[0086] In step 1), the mixture was stirred at 1200 r / min for 15 min.

[0087] Step 2) stirring at 600 r / min and then standing for 8 h;

[0088] In step 3), drying at 80° C. for 6 h;

[0089] In step 4), the temperature is raised to 500° C. and the calcination treatment is performed for 60 minutes.

[0090] Preparation Example 11

[0091] A modified biochar, which is different from Preparation Example 1 in that ferroferric oxide is replaced by an equal mass of ferrous sulfate, that is, the amount of ferroferric oxide used is 0 kg, and the amount of ferrous sulfate used is 6 kg.

[0092] Preparation Example 12

[0093] A modified biochar, which is different from Preparation Example 1 in that cobalt tetroxide is replaced by an equal mass of cobalt nitrate, that is, the amount of cobalt tetroxide used is 0 kg, and the amount of cobalt nitrate used is 10 kg.

[0094] Preparation Example 13

[0095] A modified biochar, which is different from Preparation Example 1 in that nickel oxide is replaced by an equal mass of nickel nitrate, that is, the amount of nickel oxide used is 0 kg, and the amount of nickel nitrate used is 4 kg.

[0096] Preparation Example 14

[0097] A modified biochar, which is different from Preparation Example 1 in that the amount of ferrosoferric oxide used is 4 kg, the amount of cobalt oxide used is 6 kg, and the amount of nickel oxide used is 10 kg.

[0098] Example

[0099] Example 1

[0100] A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation comprises the following steps:

[0101] Step a): Screening: The soil to be treated is naturally air-dried, and then large particles of debris are removed, and then passed through a 20 mm nylon sieve to obtain pre-treated soil.

[0102] Step b): Scrubbing: Scrubbing the pretreated soil, adding a treatment agent and mixing with water into a soil leaching machine to form a leaching solution, and the leaching solution is fully in contact with the pretreated soil to form a mixture.

[0103] The treatment agent is prepared by uniformly mixing 100 parts of modified biochar from Preparation Example 1, 250 parts of activated carbon, and 70 parts of persulfate.

[0104] The weight ratio of the treatment agent to the pretreated soil is 1:100; the solid-liquid ratio of the pretreated soil to water is 1:1.5.

[0105] Step c): Primary vibration: The mixed material is screened by a primary hydraulic vibrating screen, the particle size of the material on the screen is 5-20 mm, and the particle size of the material under the screen is less than or equal to 5 mm. The material on the screen continues to return to the scrubbing step for processing, and the material under the screen undergoes secondary vibration.

[0106] Step d): Secondary vibration: The undersize of the primary vibration is screened by a secondary hydraulic vibration screen, and the particle size of the oversize is 2-5 mm, and the particle size of the undersize is less than or equal to 2 mm. The oversize continues to return to the primary vibration or scrubbing step for processing.

[0107] Step e): The screened material of the secondary vibration is transported to the magnetic field for magnetic separation to recover the modified biochar. The material after magnetic separation enters the concentration tank for concentration, and the supernatant enters the water treatment system for treatment and reuse or discharge after meeting the standards, and the mud is discharged after passing the test.

[0108] Example 2

[0109] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 2.

[0110] Example 3

[0111] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 3.

[0112] Example 4

[0113] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 4.

[0114] Example 5

[0115] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 5.

[0116] Example 6

[0117] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 6.

[0118] Example 7

[0119] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 7.

[0120] Example 8

[0121] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 8.

[0122] Example 9

[0123] A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar is derived from Preparation Example 9;

[0124] The treatment agent includes 100 parts of modified biochar, 55 parts of persulfate and 300 parts of activated carbon.

[0125] Example 10

[0126] A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation, which is different from Example 1 in that:

[0127] The modified biochar was derived from Preparation Example 10;

[0128] The treatment agent includes 120 parts of modified biochar, 80 parts of persulfate and 200 parts of activated carbon.

[0129] During scrubbing in step b), the solid-to-liquid ratio of the soil to be treated and water is 1:1.2.

[0130] Embodiment 11

[0131] A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation, which is different from Example 1 in that the activated carbon in the treatment agent is replaced by quartz sand, that is, 250 parts of quartz sand and 0 parts of activated carbon.

[0132] Comparative Example

[0133] Comparative Example 1

[0134] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 11.

[0135] Comparative Example 2

[0136] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar comes from Preparation Example 12.

[0137] Comparative Example 3

[0138] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which differs from Example 1 in that the modified biochar comes from Preparation Example 13.

[0139] Comparative Example 4

[0140] A method for treating semi-volatile organic contaminated soil by enhanced chemical oxidation, which differs from Example 1 in that the modified biochar comes from Preparation Example 14.

[0141] Comparative Example 5

[0142] A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation, which is different from Example 1 in that the modified biochar is 70 parts and the persulfate is 100 parts.

[0143] Performance testing

[0144] 1. Recovery rate of modified biochar:

[0145] Step 01): Add 10 g of the modified biochar of Examples 1-11 and Comparative Examples 1-5 to 1 kg of soil, respectively, and stir evenly.

[0146] Step 02): Spread the soil containing modified biochar on a 30*30 cm glass plate.

[0147] Step 03): Hang a magnet with a size of 30*30*1cm 10cm above the top of the soil for 30s.

[0148] Step 04): Weigh the weight of the modified biochar absorbed by the magnet and calculate the recovery rate according to the following formula.

[0149] 2. Semi-volatile organic compound detection:

[0150] 1) Preparation of control soil samples:

[0151] Step a): Screening: The soil to be treated is naturally air-dried, and then large particles of debris are removed, and then passed through a 20 mm nylon sieve to obtain pre-treated soil.

[0152] Step b): Scrubbing: Scrubbing the pretreated soil, adding a treatment agent and mixing with water into a soil leaching machine to form a leaching solution, and the leaching solution is fully in contact with the pretreated soil to form a mixture.

[0153] The treating agent is sand and gravel.

[0154] Step c): separating the solid and liquid of the mixture to obtain a control soil.

[0155] 2) Samples to be tested:

[0156] The mixed materials that were scrubbed only once in Example 1-11 and Comparative Example 1-5 were separated into solid and liquid to obtain samples to be tested.

[0157] Testing standards: Refer to HJ 834-2017 "Determination of semi-volatile organic compounds in soil and sediment by gas chromatography-mass spectrometry" to test the control sample and the sample to be tested, and record the removal rate of aniline and 2-chlorophenol. A high removal rate means a good purification effect.

[0158] The test results of the above experiments 1-2 are detailed in Table 1.

[0159] Table 1

[0160]

[0161] According to the comparison of the test results of Examples 1, 2, 9, 10 and Comparative Examples 1-3 in Table 1, when the prepared modified biochar lacks any one of ferroferric oxide, cobalt oxide, and nickel oxide, the performance of the prepared modified activated carbon will decrease. Regarding the use of ferrous sulfate but not obtaining a modified biochar with similar performance to that of ferroferric oxide, the inventor speculates that it may be because ferrous sulfate and ferroferric oxide are connected to the carbon skeleton in different forms, resulting in a large difference in magnetism. In terms of recovery effect, the modified biochar lacking ferroferric oxide is more obviously affected by the lack of cobalt oxide and nickel oxide in terms of recovery rate; in terms of the removal effect of semi-volatile organic compounds, the lack of cobalt oxide and nickel oxide is more obvious than the lack of ferroferric oxide. It shows that the magnetic aspect mainly depends on ferroferric oxide, but ferroferric oxide may also exist in coordination with other raw materials, so the recovery on semi-volatile organic compounds will also be affected. Combined with the test data of Comparative Example 4, it can be seen that ferroferric oxide, cobalt trioxide and nickel oxide need to be used in combination in a specific proportion within a specific dosage, otherwise the combination effect cannot be fully exerted.

[0162] According to the comparison of the test results of Examples 1 and 2 with Examples 3 and 4 in Table 1, it can be seen that the recovery rate and semi-volatile organic matter removal rate of Examples 3 and 4 have a certain downward trend compared with Examples 1 and 2. The inventor speculates that it may be because the sludge and the waste rice bran are combined and recarbonized at a specific ratio to form a certain special structure, which can make ferroferric oxide, cobalt trioxide, and nickel oxide better cooperate with the system, so it is beneficial to improve the performance of modified biochar. Similarly, after the ratio between cobalt trioxide and nickel oxide changes, it will also affect the coordination effect with the system.

[0163] According to the comparison of the test results of Examples 1 and 2 with Examples 6-8 in Table 1, it can be seen that the parameters of several steps in the preparation of modified biochar are very important. If they are changed at will, the structure obtained by carbonization will be affected, and then the catalytic effect of the modified biochar as a whole will be affected. The inventor speculates that the combination of raw materials such as ferroferric oxide, cobalt trioxide, nickel oxide and sludge may be different from that in the prior art. It may be dispersed in the system by high-speed rotation and then attached to the pore structure of the modified biochar.

[0164] According to the comparison of the test results of Examples 1 and 2 with Example 11 in Table 1, it can be seen that after omitting the activated carbon, the removal effect of the treatment agent on semi-volatile organic matter is reduced. This is because the activated carbon can preferentially remove a part of the volatile organic matter, so that the persulfate can focus on preferentially treating the semi-volatile organic matter, thereby improving the purification effect on the soil.

[0165] According to the comparison of the test results of Examples 1 and 2 with Comparative Example 5 in Table 1, it can be seen that the usage ratio between modified biochar and persulfate is also very important. If they are not combined within a specific ratio, the persulfate is not fully and effectively catalyzed and semi-volatile organic compounds cannot be efficiently removed.

[0166] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for treating semi-volatile organic polluted soil by enhanced chemical oxidation, characterized in that: The following steps are involved: Screening: Screen the soil to be treated into large particles to remove large impurities; Scrubbing: Add the treatment agent and mix it with the soil to be treated to form a mixture; the ratio of the treatment agent to the soil to be treated is 1:100 by weight; the treatment agent includes the following raw materials by weight: 100-120 parts of modified biochar and 55-80 parts of persulfate; The modified biochar includes the following raw materials in parts by weight: 70-80 parts of sludge, 20-30 parts of waste rice bran, 5-10 parts of ferric oxide, 10-12 parts of cobalt oxide, 2-4 parts of nickel oxide, and 50-70 parts of water; Primary vibration, secondary vibration; The undersize material of the secondary vibration is subjected to magnetic separation to recover the modified biochar; After the soil is tested and found to be qualified, it is discharged; The preparation method of the modified biochar comprises the following steps: Mixing ferroferric oxide, cobalt trioxide, nickel oxide and water, and stirring at 1000-1200 r / min until uniform, to obtain a solution for use; The liquid to be used is mixed with the sludge and the waste rice bran at 600-800 r / min until uniform, and then allowed to stand for 2-8 hours; Then dry at 50-80°C for 6-12h to obtain a semi-finished product; The semi-finished product is placed under anaerobic conditions and calcined at 350-500° C. for 60-120 minutes to obtain modified biochar.

2. The method for treating semi-volatile organic polluted soil by enhanced chemical oxidation according to claim 1, characterized in that: The treating agent also includes 200-300 parts of activated carbon.

3. The method for treating semi-volatile organic polluted soil by enhanced chemical oxidation according to claim 1, characterized in that: When the semi-finished product is calcined, it is transferred to a nitrogen protective atmosphere with a heating rate of 10-12°C / min until it is heated to 350-500°C.

4. The method for treating semi-volatile organic polluted soil by enhanced chemical oxidation according to claim 1, characterized in that: The particle size of the ferrosoferric oxide is 20-50 μm.

5. The method for treating semi-volatile organic polluted soil by enhanced chemical oxidation according to claim 1, characterized in that: During the scrubbing, the solid-to-liquid ratio of the soil to be treated and water is 1:(1.2-1.5).

6. The method for treating semi-volatile organic polluted soil by enhanced chemical oxidation according to claim 1, characterized in that: The preparation method of the treatment agent comprises the following steps: mixing the raw materials and stirring them until they are uniform.

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