Construction process for ex-situ chemical oxidation remediation of high-viscosity organic contaminated soil

Abstract

The application provides a construction process for ex-situ chemical oxidation remediation of high-viscosity organic contaminated soil, and comprises the following steps: adding quicklime and inorganic porous structure material into the organic contaminant, crushing and screening after mixing and stirring; adding biochar, crushing and screening after mixing and stirring again; spreading the product obtained in the previous step, and turning and stirring; adding humic acid, organic waste mixture and peroxymonosulfate into the mixture after the previous step, and mixing and stirring uniformly; and curing under natural conditions. The application solves the problem of high viscosity and high water content of the organic contaminated soil by controlling the adding sequence of different reagents, reduces the water content of the clay soil, makes the clay soil loose, and makes the organic contaminant in the clay soil be oxidized by the oxidation reagent, so that the remediation effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of organic contaminated soil remediation technology, and in particular to a construction process for ex-situ chemical oxidation remediation of highly viscous organic contaminated soil. Background Technology

[0002] Soils in South China are characterized by high viscosity and low permeability. Highly viscous soils contaminated with organic pollutants, due to their high water content and strong viscosity, are very difficult to reduce in moisture content and loosen, thus affecting the efficiency of chemical oxidation remediation. Reducing moisture content and altering the aggregate structure through construction techniques to make it easier for chemical oxidants to react with organic pollutants is a crucial technology that needs to be addressed to eliminate soil organic pollution. Furthermore, the ex-situ chemical oxidation construction process for highly viscous organically contaminated soils also significantly impacts the remediation effect. Summary of the Invention

[0003] The main objective of this invention is to provide a construction process for ex-situ chemical oxidation remediation of highly viscous organic contaminated soil, which solves the problem that the soil is difficult to loosen due to its high viscosity, low permeability coefficient, and high water content, thus affecting the efficiency of chemical oxidation remediation.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a construction process for ex-situ chemical oxidation remediation of highly viscous organic contaminated soil, comprising the following steps:

[0005] S1. Add quicklime and inorganic porous materials to organic contaminated soil, mix and stir evenly with organic contaminated soil, and then crush and screen the soil through crushing and screening equipment to achieve a particle size ≤50mm.

[0006] S2. Based on step S1, add biochar, mix and stir evenly again, and then crush and screen through crushing and screening equipment to achieve a particle size ≤40mm.

[0007] S3. Spread the product obtained in step S2, and stir and turn it during the spreading process.

[0008] S4. After the treatment in step S3, add humic acid, organic waste mixture and persulfate to the mixture after the treatment in step S3, and mix and stir evenly.

[0009] S5. Maintenance under natural conditions;

[0010] The above steps enable the remediation of highly viscous organic contaminated soil.

[0011] In the preferred embodiment, in step S1, the quicklime is powder that has passed through a 200-mesh sieve, and the calcium oxide content is above 80wt%. The mass ratio of quicklime, inorganic porous material and organic contaminated soil is (1-5):(1-5):100.

[0012] In a preferred embodiment, the inorganic porous material in step S1 includes, but is not limited to, coal slag, perlite, and organic bentonite.

[0013] In the preferred embodiment, in step S2, the mass ratio of biochar to organically contaminated soil is (5-10):100.

[0014] In the preferred embodiment, the crushing and screening process in steps S1 and S2 shall be performed at least three times.

[0015] In the preferred embodiment, in step S3, the product obtained by mixing and stirring in step S2 is spread out with a thickness of no more than 0.5m, and turned and stirred once a day for no less than 3 days.

[0016] In the preferred embodiment, in step S4, the mass ratio of the humic acid, the mixture of organic waste and persulfate to the organic contaminated soil is (1-2):(5-10):(1-5):100.

[0017] In the preferred embodiment, the stirring is performed at least twice in step S4.

[0018] In the preferred embodiment, in step S5, the curing time is from the time the previous step of mixing is evenly until the end of the curing process, and the curing time is not less than 7 days.

[0019] This invention provides an ex-situ chemical oxidation remediation process for highly viscous organic polluted soil. Its beneficial effects are: (1) reducing the water content of highly viscous soil and changing the soil aggregate structure to make it loose; (2) by controlling the process steps, the agent is stirred more evenly, which is more conducive to reacting with organic pollutants, thereby eliminating pollutants; (3) by adding the agent in a certain order, first carrying out the low-cost improvement, adding quicklime, which can improve the soil quality to a certain extent, and then carrying out more in-depth improvement as needed, which can save costs and avoid unnecessary waste caused by excessive use of high-cost substances such as biochar and persulfate. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0021] Figure 1 This is a flowchart of the implementation steps of the method of the present invention. Detailed Implementation

[0022] like Figure 1 As shown, an ex-situ chemical oxidation remediation process for highly viscous organically contaminated soil includes the following steps:

[0023] S1. Add quicklime and inorganic porous materials to organic contaminated soil, mix and stir evenly with organic contaminated soil, and then crush and screen the soil through crushing and screening equipment to achieve a particle size ≤50mm.

[0024] S2. Based on step S1, add biochar, mix and stir evenly again, and then crush and screen through crushing and screening equipment to achieve a particle size ≤40mm.

[0025] S3. Spread the product obtained in step S2, and stir and turn it during the spreading process.

[0026] S4. After the treatment in step S3, add humic acid, organic waste mixture and persulfate to the mixture after the treatment in step S3, and mix and stir evenly.

[0027] S5. Maintenance under natural conditions;

[0028] The above steps enable the remediation of highly viscous organic contaminated soil.

[0029] This invention provides an ex-situ chemical oxidation remediation process for highly viscous organically contaminated soil. This process significantly reduces the moisture and viscosity of highly viscous, high-moisture soils, improves soil aeration and drainage, and promotes plant growth. Simultaneously, the addition of quicklime, biochar, and persulfate increases the soil's nitrogen and phosphorus uptake capacity, enhances nutrient availability, and reduces the toxicity and persistent pollution caused by organic pollutants. Furthermore, the sequential addition of these substances—starting with lower-cost improvements like quicklime to improve soil quality to a certain extent, followed by more in-depth improvements as needed—saves costs and avoids unnecessary waste caused by excessive use of high-cost substances such as biochar and persulfate. The method of this invention is simple to operate, highly effective, and the various substances complement each other, exerting a synergistic effect to comprehensively improve soil quality.

[0030] In the preferred embodiment, in step S1, the quicklime is powder that has passed through a 200-mesh sieve, and the calcium oxide content is above 80wt%. The mass ratio of quicklime, inorganic porous material and organic contaminated soil is (1-5):(1-5):100.

[0031] Using quicklime that has passed through a 200-mesh sieve ensures that the added quicklime particles are very fine, allowing for better mixing with the soil. This increases the contact area with acidic substances in the soil, improving the efficiency of the neutralization reaction. Furthermore, the quicklime particles passing through the 200-mesh sieve are more uniform, reducing the likelihood of them flying away during use and minimizing environmental pollution. A calcium oxide content of over 80wt% further enhances the neutralizing ability of the quicklime, making it even more conducive to the neutralization reaction between quicklime and acidic substances in the soil.

[0032] Quicklime generates a large amount of heat when it reacts with moisture in the soil. This high-temperature property can be used to kill pests and diseases in the soil, eliminate or reduce heavy metal ion pollution, replenish nutrients such as calcium and magnesium, regulate soil pH, and increase soil pH. Furthermore, quicklime can increase the molecular tension of water, causing it to solidify and thus improving the soil's aggregate structure, thereby reducing the moisture content of the mixture, activating the soil, and alleviating soil compaction.

[0033] Using a specific ratio of quicklime to organically contaminated soil helps control the soil's pH level within a suitable range.

[0034] In a preferred embodiment, the inorganic porous material in step S1 includes, but is not limited to, cinder, perlite, and organo-bentonite. Adding these inorganic porous materials can further improve the soil's pore structure and aeration. Furthermore, the porous material has a large specific surface area, providing more adsorption sites and competing for moisture and organic pollutants in the soil, thus contributing to soil embrittlement.

[0035] In the preferred embodiment, in step S2, the mass ratio of biochar to organically contaminated soil is (5-10):100. Biochar has a large specific surface area, well-developed pore structure, and high cation exchange capacity, which can improve the physical and chemical properties of soil. Biochar can increase the soil's nitrogen and phosphorus adsorption capacity, soil organic matter content, and soil nutrient availability, promoting the absorption of nitrogen and phosphorus by crops. Simultaneously, biochar can also alter the soil's tensile strength, hydrodynamic properties, and gas transport capacity, which is beneficial for seed germination and invertebrate movement in the soil.

[0036] In the preferred embodiment, the crushing and screening process in steps S1 and S2 shall be performed at least three times.

[0037] In the preferred embodiment, in step S3, the product obtained from mixing and stirring in step S2 is spread out to a thickness of no more than 0.5 m, and turned over and stirred once a day for no less than 3 days. Spreading and turning over and stirring are beneficial to soil aeration and drainage, can prevent soil compaction and reduce moisture content, and can further ensure that the agent is evenly mixed with the contaminated soil and reacts.

[0038] In the preferred embodiment, in step S4, the mass ratio of the humic acid, the mixture of organic waste and persulfate to the organic contaminated soil is (1-2):(5-10):(1-5):100.

[0039] Persulfate has strong oxidizing properties, which can increase the nitrogen and phosphorus adsorption capacity in the soil, change the distribution of organic pollutants in the soil, and improve the decomposability of organic pollutants, thereby reducing the toxicity and persistent pollution caused by organic pollutants. This can also reduce soil moisture and viscosity to a certain extent. In addition, by adjusting the ratio of persulfate to organic polluted soil, the process and effect of oxidation reaction can be better controlled, avoiding the adverse effects of excessive use on soil and environment.

[0040] The fermentation of humic acid and organic waste mixtures generates high temperatures, which can activate persulfate to release free radicals, thereby improving the persulfate oxidation efficiency. Furthermore, humic acid is a natural activator, reducing treatment costs and avoiding the secondary pollution problems that may be caused by the use of chemical agents. At the same time, the products of the fermentation of humic acid and organic waste mixtures can be used as organic fertilizer, which not only increases fertility and aeration but also further alleviates soil compaction.

[0041] In the preferred embodiment, the stirring is performed at least twice in step S4.

[0042] In the preferred embodiment, in step S5, the curing time is from the time of thorough mixing in the previous step until the end of curing, and the curing time shall not be less than 7 days. The natural condition curing specifically includes: under normal temperature and pressure conditions, allowing the soil to remain undisturbed, enabling the persulfate to react with the organic pollutants in the contaminated soil through an oxidation reaction. Furthermore, if the curing time is too short, the degradation rate of organic pollutants will be low; if the curing time is too long, it will increase the construction cycle.

[0043] Example 1

[0044] Step 1: High-moisture, highly viscous soil excavated from the organically contaminated site is transported to the remediation shed. Quicklime is spread on the surface of the contaminated soil and mixed. The high-viscosity organically contaminated soil has a moisture content of over 60% and a benzo[a]pyrene concentration of 6.85 mg / kg. After the organically contaminated soil is evenly mixed with quicklime and cinder, it is crushed and sieved three times through a crushing and screening hopper, while further mixing the organically contaminated soil with quicklime and stirring. The quicklime is powder that has passed through a 200-mesh sieve and has a calcium oxide content of over 80 wt%. The mass ratio of quicklime, cinder, and organically contaminated soil is (1-5):(1-5):100.

[0045] Step 2: Add biochar and mix. The mixture is crushed and sieved three times using a crushing and screening hopper, while simultaneously further mixing the organic contaminated soil and biochar ash until homogeneous. The mass ratio of biochar to organic contaminated soil is (5-10):100.

[0046] Step 3: Mix the two agents mentioned above with the organic contaminated soil using a mixer, then crush and sieve the mixture. Spread it out on a temporary storage area to a thickness not exceeding 0.5m. Turn the mixture over once a day to further mix it evenly, and allow it to air dry naturally to reduce its moisture content and allow the agents to react with the contaminated soil. Turn the mixture over three times a day until the moisture content is reduced to below 40%, the pH value is not lower than 8, and the particle size is less than 30mm.

[0047] Step 4: Add humic acid, the organic waste mixture, and persulfate, and mix thoroughly. Stir twice using a crushing and screening hopper. The mass ratio of humic acid, the organic waste mixture, and persulfate to the organically contaminated soil is (1-2):(5-10):(1-5):100.

[0048] Step 5: Natural condition maintenance, from adding humic acid, organic waste mixture and persulfate and stirring evenly until the end of maintenance, is 7 days.

[0049] Example 2

[0050] The difference between this embodiment and Embodiment 1 is that the crushing and screening process in step one is performed five times. The remaining steps and parameters are the same as in Embodiment 1.

[0051] Example 3

[0052] The difference between this embodiment and Embodiment 1 is that the crushing and screening process in step two is repeated 5 times. The remaining steps and parameters are the same as in Embodiment 1.

[0053] Example 4

[0054] The difference between this embodiment and Embodiment 1 is that the paving thickness in step three is 0.3m. The remaining steps and parameters are the same as in Embodiment 1.

[0055] Example 5

[0056] The difference between this embodiment and Embodiment 1 is that the number of times the tossing is performed in step three is 5. The remaining steps and parameters are the same as in Embodiment 1.

[0057] Example 6

[0058] The difference between this embodiment and Embodiment 1 is that the stirring is performed 4 times in step four. The remaining steps and parameters are the same as in Embodiment 1.

[0059] Example 7

[0060] The difference between this embodiment and Embodiment 1 is that, in step five, the time from adding persulfate and stirring evenly to the end of curing is 10 days. The remaining steps and parameters are the same as in Embodiment 1.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that the crushing and screening process in step one is performed only once. The remaining steps and parameters are the same as in Example 1.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that the crushing and screening process in step two is performed only once. The remaining steps and parameters are the same as in Example 1.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that the paving thickness in step three is 1.0 m. The remaining steps and parameters are the same as in Example 1.

[0067] Comparative Example 4

[0068] The difference between this comparative example and Example 1 is that the number of times the tossing is performed in step three is 1. The remaining steps and parameters are the same as in Example 1.

[0069] Comparative Example 5

[0070] The difference between this comparative example and Example 1 is that the stirring in step four is performed once. The remaining steps and parameters are the same as in Example 1.

[0071] Comparative Example 6

[0072] The difference between this comparative example and Example 1 is that the time from adding humic acid, the mixture of organic waste, and persulfate and stirring evenly to the end of the curing process is 3 days. The remaining steps and parameters are the same as in Example 1.

[0073] Comparative Example 7

[0074] The difference between this comparative example and Example 1 is that the order of steps one and two is reversed. The remaining steps and parameters are the same as in Example 1.

[0075] Comparative Example 8

[0076] The difference between this comparative example and Example 1 is that the order of steps one and three is reversed. The remaining steps and parameters are the same as in Example 1.

[0077] Comparative Example 9

[0078] The difference between this comparative example and Example 1 is that the order of steps one and four is reversed. The remaining steps and parameters are the same as in Example 1.

[0079] Comparative Example 10

[0080] The difference between this comparative example and Example 1 is that the order of steps two and three is reversed. The remaining steps and parameters are the same as in Example 1.

[0081] Comparative Example 11

[0082] The difference between this comparative example and Example 1 is that the order of steps two and four is reversed. The remaining steps and parameters are the same as in Example 1.

[0083] Comparative Example 12

[0084] The difference between this comparative example and Example 1 is that the order of steps three and four is reversed. The remaining steps and parameters are the same as in Example 1.

[0085] Comparative Example 13

[0086] The difference between this comparative example and Example 1 is that the substances added in steps one, two and three are added to the organically contaminated soil simultaneously as the first step, while the remaining steps are performed in the same order and with the same parameters as in Example 1.

[0087] Table 1

[0088] Specific examples of detection indicators Benzo[a]pyrene concentration after treatment (mg / kg) Repair and removal rate % Example 1 0.43 93.72% Example 2 0.31 95.47% Example 3 0.33 95.18% Example 4 0.30 95.62% Example 5 0.28 95.91% Example 6 0.29 95.77% Example 7 0.40 94.16% Comparative Example 1 0.85 87.59% Comparative Example 2 0.89 87.01% Comparative Example 3 0.92 86.57% Comparative Example 4 0.88 87.15% Comparative Example 5 0.76 88.91% Comparative Example 6 0.63 90.80% Comparative Example 7 0.90 86.86% Comparative Example 8 0.75 89.05% Comparative Example 9 1.21 82.34% Comparative Example 10 0.69 89.93% Comparative Example 11 0.94 86.28% Comparative Example 12 0.86 87.45% Comparative Example 13 1.77 74.16%

[0089] The target value for benzo[a]pyrene repair is 0.55 mg / kg.

[0090] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A construction process for ex-situ chemical oxidation remediation of highly viscous organically contaminated soil, characterized by: Includes the following steps: S1. Add quicklime and inorganic porous materials to organic contaminated soil, mix and stir evenly with organic contaminated soil, and then crush and screen the soil through crushing and screening equipment to achieve a particle size ≤50mm. S2. Based on step S1, add biochar, mix and stir evenly again, and then crush and screen through crushing and screening equipment to achieve a particle size ≤40mm. S3. Spread the product obtained in step S2, and stir and turn it during the spreading process. S4. After the treatment in step S3, add humic acid, organic waste mixture and persulfate to the mixture after the treatment in step S3, and mix and stir evenly. S5. Maintenance under natural conditions; The above steps are used to remediate highly viscous organic contaminated soil. In step S1, quicklime is powder that passes through a 200-mesh sieve and has a calcium oxide content of more than 80 wt%. The mass ratio of quicklime, inorganic porous material and organic contaminated soil is (1-5):(1-5):

100. The inorganic porous material includes cinder, perlite and organic bentonite. In steps S1 and S2, the crushing and screening process is no less than 3 times. In step S3, the product obtained from mixing and stirring in step S2 is spread out with a thickness of no more than 0.5m, and is turned and stirred once a day for no less than 3 days. In step S4, the mass ratio of the humic acid, the organic waste mixture, and the persulfate to the organic contaminated soil is (1-2):(5-10):(1-5):100; In step S4, the stirring is performed at least twice.

2. The ex-situ chemical oxidation remediation construction process for highly viscous organically contaminated soil according to claim 1, characterized in that: In step S2, the mass ratio of biochar to organic contaminated soil is (5-10):

100.

3. The ex-situ chemical oxidation remediation construction process for highly viscous organically contaminated soil according to claim 1, characterized in that: In step S5, the curing time is from the time the previous step was mixed evenly until the curing is completed, and the curing time shall not be less than 7 days.

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