Method for directly oxidizing petroleum hydrocarbon in soil through in-situ regulation and control of soil polarity Fenton

Abstract

The invention discloses a method for directly oxidizing petroleum hydrocarbon in soil through in-situ regulation and control of soil polarity Fenton, which comprises the following steps: fully mixing a hydrophilic organic matter and ferric salt to prepare a soil polarity regulation and control solution, adding the prepared soil polarity regulation and control solution into petroleum-contaminated soil, and regulating and controlling the polarity of the petroleum-contaminated soil through oscillation; hydrogen peroxide is added for continuous oscillation, and petroleum hydrocarbon in the petroleum-contaminated soil is efficiently and directly oxidized. According to the method, Fenton degradation of petroleum hydrocarbon in soil is enhanced, and the petroleum hydrocarbon can be removed to the maximum extent by means of polarity regulation and control; after the soil is regulated and controlled, the polarity of the soil is enhanced, petroleum hydrocarbon in the soil is directly oxidized, and the Fenton oxidation capacity of the petroleum hydrocarbon in the soil is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of in-situ remediation of petroleum-contaminated soil and relates to a method for in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in the soil by Fenton. Background Art

[0002] The petroleum hydrocarbons that accidentally enter the environment during oil extraction, refining, transportation and storage have formed a large amount of petroleum hydrocarbon contaminated soil. It has now become a difficult problem in the field of domestic environmental remediation. Fenton technology has attracted the attention of many researchers in the field of chemical remediation due to its convenient operation and fast effectiveness. Among them, in-situ chemical oxidation technology has a fast effect and great potential for site remediation, and is one of the most widely used technologies. Therefore, it is very necessary to develop a new Fenton technology suitable for in-situ remediation of petroleum hydrocarbon contaminated soil.

[0003] At present, most of the Fenton oxidation technologies for petroleum hydrocarbon soils are based on liquid phase free radical reactions. However, petroleum hydrocarbons are combined with soil for a long time and are highly hydrophobic, so the reaction capacity of the added Fenton reagent is very limited. Free radicals in the liquid phase exist for a short time and are easily captured by organic matter, small molecules, soil impurities, etc. in the soil, resulting in ineffective consumption. This is the reason why the Fenton method for oxidizing petroleum hydrocarbons in soil is currently inefficient. Similarly, this also leads to the fact that soil remediation often requires the addition of a large amount of reagents to increase efficiency, or the use of other synergistic technologies to strengthen the Fenton process. If free radicals can be directly oxidized in the solid phase of the soil where petroleum hydrocarbons are located, the efficiency of Fenton remediation will be greatly improved, and reagent costs can also be saved. Summary of the invention

[0004] In order to solve the above defects existing in the prior art, the purpose of the present invention is to provide a method for in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in the soil by Fenton. By introducing hydrophilic organic matter with hydrophilic functional groups CH, CO, C=O, the hydrophilicity and polarity of the soil are enhanced. The OH is promoted to transfer from the liquid phase to the solid phase to directly oxidize the petroleum hydrocarbons. The utilization rate of hydrogen peroxide is improved, thereby achieving the purpose of efficient Fenton direct oxidation of petroleum hydrocarbons in the soil.

[0005] The present invention is achieved through the following technical solutions.

[0006] In one aspect, the present invention provides a method for in-situ regulation of soil polarity Fenton direct oxidation of petroleum hydrocarbons in soil, comprising the following steps:

[0007] Step 1, adding 40 to 60 parts of distilled water and 0.3 to 1.0 parts of iron salt to 3 to 6 parts of hydrophilic organic matter according to a mass ratio, mixing evenly, to obtain a soil polarity regulating solution;

[0008] Step 2, mixing the soil polarity regulating solution with the petroleum contaminated soil in a mass ratio of 1:(10-15), and placing the mixture in a cyclotron to oscillate and regulate the polarity of the soil;

[0009] Step 3, adding hydrogen peroxide to the petroleum-contaminated soil after shaking control at a mass ratio of 100:(5-18), and shaking continuously, thereby completing the process of in-situ control of soil polarity Fenton direct oxidation of petroleum hydrocarbons in the soil.

[0010] Step 3, according to the mass ratio of hydrogen peroxide to soil of (5-18):100, hydrogen peroxide is added to the petroleum-contaminated soil after shaking control and continuously shaken, that is, the process of in-situ control of soil polarity Fenton direct oxidation of petroleum hydrocarbons in the soil is completed.

[0011] Preferably, the hydrophilic organic matter is chitosan, humic acid or fulvic acid.

[0012] Preferably, the iron salt is ferrous sulfate, ferrous chloride or ferrous oxalate, and the molar concentration of the iron salt is 3 to 8 mmol / L.

[0013] Preferably, the total petroleum hydrocarbon content in the high-oil soil in the petroleum contaminated soil is 9.76 g / kg, and the total petroleum hydrocarbon content in the low-oil soil is 3.0 g / kg.

[0014] Preferably, the cyclotron rotation speed is 160-180 r / min, and the time for the petroleum-contaminated soil to be in full contact with the soil polarity regulating liquid is 20-60 min.

[0015] Preferably, the molar concentration of the iron salt is 3-8 mmol / L.

[0016] Preferably, the mass fraction of the hydrogen peroxide is 30% to 35%.

[0017] Preferably, hydrogen peroxide is added to the soil after shaking and the soil is shaken continuously for 24 to 36 hours.

[0018] Preferably, the degradation amount of alkanes in the soil by the polarity control group is not less than 4398.42 mg / kg; the degradation amount of petroleum hydrocarbons by a unit of hydrogen peroxide is not less than 37.97 mg / g.

[0019] On the other hand, the present invention provides a soil polarity regulating solution used in the method, comprising the following raw materials in the following mass ratios: 3.0-6.0 parts of hydrophilic organic matter, 0.3-1.0 parts of iron salt, and 40-60 parts of distilled water.

[0020] The present invention adopts the above technical solution, which has the following beneficial effects:

[0021] 1. The present invention uses hydrophilic organic matter, iron salt, and distilled water to fully mix and configure a soil polarity regulating solution, which changes the soil polarity after fully contacting with petroleum hydrocarbon contaminated soil. The increased soil polarity can achieve the regulation of hydroxyl radicals and guide the hydroxyl radicals to efficiently and directly oxidize petroleum hydrocarbons in the soil solid phase.

[0022] 2. The increase in soil polarity is attributed to the substantial increase in hydrophilic organic matter (humic acid-like substances) and hydrophilic functional groups CO, C=O, OH in the soil. The increase in the proportion of these two components can continuously enhance the hydrophilicity of the soil, and the hydroxyl radicals in the water phase will gradually transfer from the liquid phase to the solid phase, promoting the participation of hydroxyl radicals in the solid phase to directly oxidize petroleum hydrocarbons.

[0023] 3. The increase in soil polarity can promote the direct oxidation of petroleum hydrocarbons in the soil solid phase by hydroxyl radicals. This solution greatly enhances the utilization rate of free radicals and avoids the loss of free radicals during migration and diffusion in the traditional Fenton process. Most importantly, the direct generation of hydroxyl radicals in the solid phase can improve the selectivity of the hydroxyl radicals involved in the reaction and directly participate in the subsequent oxidation reaction.

[0024] 4. The present invention is used to increase the direct oxidation amount of petroleum hydrocarbons in the soil. After polarity regulation, the Fenton oxidation amount of petroleum hydrocarbons in the soil can reach 4398.42-6220.20 mg / kg, which is higher than the traditional Fenton oxidation amount of petroleum hydrocarbons under corresponding conditions of 2049.61-3785.65 mg / kg; after polarity regulation, the oxidation amount of petroleum hydrocarbons per unit of hydrogen peroxide is 37.97-71.86 mg / g, which is higher than the traditional Fenton technology oxidation amount of petroleum hydrocarbons per unit of hydrogen peroxide under corresponding conditions of 19.32-33.75 mg / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1(a) shows the Fourier transform infrared spectroscopy analysis of soil in polarity regulation and traditional Fenton method;

[0027] Figure 1(b) shows the analysis of the integral intensity of functional groups in soil Fourier transform infrared spectroscopy in polarity regulation and traditional Fenton method;

[0028] Figure 1(c) shows the analysis of soil functional groups and petroleum hydrocarbon oxidation in polarity regulation and traditional Fenton method;

[0029] Figure 2(a) shows the three-dimensional fluorescence spectrum analysis of organic matter distribution in the original soil;

[0030] Figure 2(b) is a three-dimensional fluorescence spectrum analysis of polarity-regulated soil organic matter distribution;

[0031] Figure 2(c) shows the three-dimensional fluorescence spectrum analysis of organic matter distribution in traditional Fenton soil;

[0032] Figure 2(d) is an analysis of the proportion of each component in the three-dimensional fluorescence spectrum of organic matter distribution in soil;

[0033] Figure 2(e) shows the distribution of organic matter in soil and the analysis of the amount of petroleum hydrocarbon oxidation;

[0034] Figure 3(a) shows the change of hydroxyl radicals over time in the polarity control strategy;

[0035] Figure 3(b) shows the variation of hydroxyl radicals over time in the traditional Fenton method;

[0036] Figure 3(c) shows the relationship between the polarity control strategy and the traditional Fenton method for the oxidation of petroleum hydrocarbons under similar hydroxyl radical conditions;

[0037] Figure 3(d) shows the relationship between the polarity control strategy and the change of hydroxyl radicals in the traditional Fenton method under similar petroleum hydrocarbon oxidation conditions;

[0038] Figure 4 is the relationship between polarity and the amount of oxidation of petroleum hydrocarbons;

[0039] Figure 5 (a) shows the relationship between the oxidation amount of petroleum hydrocarbons and the oxidation amount of petroleum hydrocarbons per unit of hydrogen peroxide after polarity regulation;

[0040] Figure 5(b) shows the relationship between the oxidation amount of petroleum hydrocarbons in the comparative example and the oxidation amount of petroleum hydrocarbons per unit of hydrogen peroxide. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0042] The present invention provides a method for in-situ regulation of soil polarity Fenton efficient direct oxidation of petroleum hydrocarbons in soil, comprising the following steps:

[0043] Step 1, preparation of soil polarity control solution:

[0044] According to the mass ratio, 3.0-6.0 parts of hydrophilic organic matter (chitosan, humic acid or fulvic acid) are uniformly mixed with 40-60 parts of distilled water, and then 0.3-1.0 parts of iron salt (ferrous sulfate, ferrous chloride or ferrous oxalate) are added, and the molar concentration of the iron salt is 3-8 mmol / L. After mixing again, a soil polarity regulating solution is obtained.

[0045] Step 2: Regulate the polarity of the soil:

[0046] The soil polarity regulating solution prepared in step 1 and the petroleum contaminated soil are added into a container in a mass ratio of 1:(10-15) for mixing, and placed on a cyclotron oscillator for oscillation, and the rotation speed of the cyclotron oscillator is 160-180r / min; the petroleum contaminated soil and the soil polarity regulating solution are fully in contact for 20-60min to ensure that the soil is fully in contact with the soil polarity regulating solution, and the polarity of the soil is oscillated to regulate.

[0047] Among them, the total petroleum hydrocarbon (TPH) content in high-oil soil of petroleum contaminated soil is 9.76g / kg, and the total petroleum hydrocarbon content in low-oil soil is 3.0g / kg.

[0048] Step 3, Fenton efficient direct oxidation of soil petroleum hydrocarbons:

[0049] Add hydrogen peroxide with a mass fraction of 30% to 35% to the soil after polarity adjustment in step 2 at a mass ratio of hydrogen peroxide to soil of (5 to 18): 100, and continue to oscillate on a cyclotron at a speed of 160 to 180 r / min for 24 to 36 hours to complete the process of in-situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in the soil.

[0050] The regulation of soil polarity can be explained by the ratio of the integrated area of ​​hydrophilic functional groups to humic acid. By adding hydrophilic organic matter, a series of hydrophilic functional groups (CH, CO, OH) on it can be used to regulate soil polarity, thereby promoting the transfer of liquid phase free radicals to the soil solid phase where petroleum hydrocarbons are located, and realizing efficient direct oxidation of petroleum hydrocarbons in the solid phase. In addition, these added hydrophilic organic matter is converted into another kind of organic matter humic acid substances commonly found in soil during the reaction. This will also improve the hydrophilicity of the soil, enhance the transfer ability of hydroxyl radicals, and increase the utilization rate of hydroxyl radicals. The final conversion of the added organic matter into humic acid substances that already exist in the soil also shows that soil polarity regulation can avoid the hidden expenses caused by subsequent pollution. The in-situ regulation characteristics can also reduce costs and ultimately achieve efficient degradation of petroleum hydrocarbons in the soil.

[0051] The following measurement method is used to verify the performance of the soil polarity regulation strategy in efficiently and directly oxidizing petroleum hydrocarbons in the soil.

[0052] The decomposition law of hydrogen peroxide was determined by titanium sulfate colorimetry using an ultraviolet-visible spectrophotometer. The residual petroleum hydrocarbons in the soil were determined by gas chromatography with a hydrogen ion flame detector, and the differences in the oxidation of petroleum hydrocarbons between the polarity control strategy and the traditional Fenton method were compared. The changes in hydroxyl radicals during the decomposition of petroleum hydrocarbons were determined by electron paramagnetic resonance spectrometry. The functional group characteristics of the soil were analyzed by Fourier transform infrared spectrometer.

[0053] The effect of the present invention on the efficient direct oxidation of soil petroleum hydrocarbons can be seen from the following aspects:

[0054] (1) Analysis of structural characteristics of soil functional groups

[0055] The polarity regulation method used in the present invention enhances the peak intensity of typical hydrophilic functional groups in soil, including the stretching vibration peak of CO (1052cm -1 , integrated intensity: 74.46), stretching vibration peak of C=O (1620cm -1 , integrated intensity: 14.89) and OH (3500cm -1 , integrated intensity: 112.92), see Figure 1(a). In the soil using the traditional Fenton technique, the intensity of the relevant hydrophilic functional group peaks is relatively low. Among them, the stretching vibration peak of CO (1052cm -1 , integrated intensity: 51.55), stretching vibration peak of C=O (1620cm -1 , integrated intensity: 3.33) and OH (3500cm -1 , integral intensity: 42.64), see Figure 1(b). The change of hydrophilic functional groups is closely related to the oxidation amount of petroleum hydrocarbons. The oxidation amount of petroleum hydrocarbons in the polarity-controlled group with a larger hydrophilic functional group area is 1005.25 mg / kg higher than that of the traditional Fenton, see Figure 1(c).

[0056] (2) Analysis of soil organic matter characteristics

[0057] The polarity regulation method used in the present invention increases the proportion of typical hydrophilic organic matter components in the soil, especially the proportion of humic acid-like components. It increased from 56.83% in the original soil to 85.77%, while the traditional Fenton method was 53.62%, see Figure 2 (a), Figure 2 (b) and Figure 2 (c). After polarity regulation, the fluorescence intensity of proteins (Ⅰ, Ⅱ) and humic acid areas (Ⅲ) significantly decreased, and the fluorescence intensity of humic acid (Ⅴ) areas significantly increased. After polarity regulation, the proportion of humic acid-like components was 85.77%, far exceeding the original soil and the traditional Fenton method. Therefore, the content of hydrophilic organic matter (humic acid-like components) was significantly increased after polarity regulation. The proportion of humic acid-like components in the polarity regulation group was 32.15% higher than that in the traditional Fenton method, and the corresponding petroleum hydrocarbon oxidation amount in the polarity regulation group was 1005.25 mg / kg higher than that in the traditional Fenton. This indicates that the increase in humic acid increases the polarity of the soil and can significantly increase the oxidation amount of petroleum hydrocarbons, see Figure 2(d) and Figure 2(e).

[0058] (3) Relationship between changes in hydroxyl radicals and petroleum hydrocarbons in polarity control strategies

[0059] The change of hydroxyl radicals over time in the polarity control strategy and the traditional Fenton method is similar, as shown in Figure 3 (a) and Figure 3 (b). Under similar total ·OH intensity conditions, the oxidation amount of petroleum hydrocarbons in the soil by H2O2 (30.73 au) and polarity control strategy (30.61 au) in the traditional Fenton method was 2143.51 mg / kg and 6220.20 mg / kg, respectively, as shown in Figure 3 (c). In addition, in the experimental group with similar petroleum hydrocarbon oxidation amount, after polarity control, ·OH was only 5.97 x 10 -2 au can oxidize 3361.10 mg / kg of petroleum hydrocarbons; while the traditional Fenton technology requires a larger amount of OH (43.35 x 10 -2 au) to oxidize 3393.61 mg / kg petroleum hydrocarbons, as shown in Figure 3(d). This demonstrates the effectiveness of the polarity regulation strategy.

[0060] (4) Relationship between polarity change and the amount of petroleum hydrocarbon oxidation

[0061] The increase in hydrophilic organic matter and functional groups are related to the oxidation amount of petroleum hydrocarbons. After regulation, the soil polarity (η=235.8, 450mmol / L, TPH oxidation amount 6220.20mg / kg) is greater than the traditional Fenton (η=181.87, 450mmol / L, TPH oxidation amount 5214.95mg / kg). This clearly shows that the TPH oxidation amount increased after the soil polarity regulation. Furthermore, the difference in polarity (Δη=53.97) is positively correlated with the oxidation amount of petroleum hydrocarbons (ΔTPH=1005.50mg / kg); η1 and the oxidation amount of petroleum hydrocarbons; η2 and the oxidation amount of petroleum hydrocarbons. This shows that polarity regulation has a promoting effect on the efficient and direct oxidation of petroleum hydrocarbons, see Figure 4 .

[0062] The present invention is further illustrated by means of specific examples below.

[0063] Embodiment 1:

[0064] The hydrophilic organic matter used is chitosan, the iron salt is ferrous sulfate, the molar concentration of ferrous sulfate is 6mmol / L, the high-oil soil is used in the petroleum contaminated soil, the total petroleum hydrocarbon content is 9.76g / kg, the rotation speed of the cyclotron oscillator is 160r / min when regulating the soil polarity, and the contact time between the soil and the soil polarity regulating solution is 40min. Fenton's efficient direct oxidation of soil petroleum hydrocarbons uses 30% hydrogen peroxide with a concentration of 450mmol / L.

[0065] (1) Preparation of soil polarity control solution: 5 parts of hydrophilic organic chitosan and 50 parts of distilled water were mixed evenly according to the mass ratio, and then 0.3 parts of ferrous sulfate were added to obtain the soil polarity control solution.

[0066] (2) Controlling soil polarity: The soil polarity control solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:12 and mixed. The mixture was placed on a cyclotron at 160 r / min for 40 min to ensure that the soil was in full contact with the soil polarity control solution.

[0067] (3) Fenton's efficient direct oxidation of petroleum hydrocarbons in soil: 30% hydrogen peroxide was added to the soil after polarity adjustment in step 2 at a hydrogen peroxide: soil mass ratio of 12:100, and the soil was continuously oscillated at 160 r / min on a cyclotron oscillator for 36 h, thus completing the process of in situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in soil.

[0068] After the reaction, the polarity control strategy can directly oxidize and remove 6220.20 mg / kg of petroleum hydrocarbons, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 67.76 mg / g, as shown in Figure 5(a).

[0069] Embodiment 2:

[0070] The hydrophilic organic matter used is fulvic acid, the iron salt is ferrous chloride, the molar concentration of ferrous chloride is 7mmol / L, the high-oil soil is used in the petroleum contaminated soil, the total petroleum hydrocarbon content is 9.76g / kg, the rotation speed of the cyclotron oscillator is 165r / min when regulating the soil polarity, and the contact time between the soil and the soil polarity regulating solution is 60min. Fenton's efficient direct oxidation of soil petroleum hydrocarbons uses 35% hydrogen peroxide with a concentration of 450mmol / L.

[0071] (1) Preparation of soil polarity control solution: 4 parts of hydrophilic organic matter fulvic acid and 60 parts of distilled water were mixed evenly according to the mass ratio, and then 0.4 parts of ferrous chloride were added to obtain the soil polarity control solution.

[0072] (2) Controlling soil polarity: The soil polarity control solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:10 and mixed. The mixture was placed on a cyclotron at 165 rpm for 60 min to ensure that the soil was in full contact with the soil polarity control solution.

[0073] (3) Fenton's efficient direct oxidation of petroleum hydrocarbons in soil: 35% hydrogen peroxide was added to the soil after polarity adjustment in step 2 at a hydrogen peroxide: soil mass ratio of 12:100, and the soil was continuously oscillated at a speed of 165 r / min for 32 h on a cyclotron oscillator, thereby completing the process of in situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in soil.

[0074] After the reaction, the polarity control strategy can directly oxidize and remove 5027.16 mg / kg of petroleum hydrocarbons, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 54.76 mg / g, as shown in Figure 5(a).

[0075] Embodiment 3:

[0076] The hydrophilic organic matter used is chitosan, the iron salt is ferrous sulfate, the molar concentration of ferrous sulfate is 3mmol / L, the high-oil soil is used in the petroleum contaminated soil, the total petroleum hydrocarbon content is 9.76g / kg, the rotation speed of the cyclotron oscillator is 180r / min when regulating the soil polarity, and the contact time between the soil and the soil polarity regulating solution is 20min. Fenton's efficient direct oxidation of soil petroleum hydrocarbons uses 35% hydrogen peroxide with a concentration of 600mmol / L.

[0077] (1) Preparation of soil polarity control solution: 6 parts of hydrophilic organic chitosan and 40 parts of distilled water were mixed evenly according to the mass ratio, and then 0.7 parts of ferrous sulfate were added to obtain the soil polarity control solution.

[0078] (2) Controlling soil polarity: The soil polarity control solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:14 and mixed. The mixture was placed on a cyclotron at 180 r / min for 20 min to ensure that the soil was in full contact with the soil polarity control solution.

[0079] (3) Fenton's efficient direct oxidation of petroleum hydrocarbons in soil: 35% hydrogen peroxide was added to the soil after polarity adjustment in step 2 at a hydrogen peroxide: soil mass ratio of 18:100, and the soil was continuously oscillated on a cyclotron at a speed of 180 r / min for 24 h, thus completing the process of in situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in soil.

[0080] After the reaction, the polarity control strategy can directly oxidize and remove 4986.65 mg / kg of petroleum hydrocarbons, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 40.73 mg / g, as shown in Figure 5(a).

[0081] Embodiment 4:

[0082] The hydrophilic organic matter used is chitosan, the iron salt is ferrous sulfate, the molar concentration of ferrous sulfate is 6mmol / L, low-oil soil is used in the petroleum contaminated soil, the total petroleum hydrocarbon content is 3.0g / kg, the rotation speed of the cyclotron oscillator is 175r / min when regulating the soil polarity, and the contact time between the soil and the soil polarity regulating solution is 50min. Fenton's efficient direct oxidation of soil petroleum hydrocarbons uses 35% hydrogen peroxide with a concentration of 600mmol / L.

[0083] (1) Preparation of soil polarity control solution: 3 parts of hydrophilic organic chitosan and 55 parts of distilled water were mixed evenly according to the mass ratio, and then 0.6 parts of ferrous sulfate were added to obtain the soil polarity control solution.

[0084] (2) Controlling soil polarity: The soil polarity control solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:14 and mixed. The mixture was placed on a cyclotron at 175 rpm for 50 min to ensure that the soil was in full contact with the soil polarity control solution.

[0085] (3) Fenton's efficient direct oxidation of petroleum hydrocarbons in soil: 35% hydrogen peroxide was added to the soil after polarity adjustment in step 2 at a mass ratio of 100:18, and the soil was continuously oscillated at a speed of 175 r / min for 28 h on a cyclotron oscillator to complete the process of in situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in soil.

[0086] (3) Fenton's efficient direct oxidation of petroleum hydrocarbons in soil: 35% hydrogen peroxide was added to the soil after polarity adjustment in step 2 at a hydrogen peroxide: soil mass ratio of 18:100, and the soil was continuously oscillated at a speed of 175 r / min for 28 h on a cyclotron oscillator, thereby completing the process of in situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in soil.

[0087] After the reaction, the polarity control strategy can directly oxidize and remove 4403.21 mg / kg of petroleum hydrocarbons, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 37.97 mg / g, as shown in Figure 5(a).

[0088] Embodiment 5:

[0089] The hydrophilic organic matter used is humic acid, the iron salt is ferrous oxalate, the molar concentration of ferrous oxalate is 8mmol / L, low-oil soil is used in petroleum-contaminated soil, the total petroleum hydrocarbon content is 3.0g / kg, the rotation speed of the cyclotron oscillator is 170r / min when regulating the soil polarity, and the contact time between the soil and the soil polarity regulating solution is 40min. Fenton's efficient direct oxidation of soil petroleum hydrocarbons uses 30% hydrogen peroxide with a concentration of 300mmol / L.

[0090] (1) Preparation of soil polarity control solution: 3 parts of hydrophilic organic matter humic acid and 45 parts of distilled water were mixed evenly according to the mass ratio, and then 1.0 part of ferrous oxalate was added to obtain the soil polarity control solution.

[0091] (2) Controlling soil polarity: The soil polarity control solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:15 and mixed. The mixture was placed on a cyclotron at 170 r / min for 40 min to ensure that the soil was in full contact with the soil polarity control solution.

[0092] (3) Fenton's efficient direct oxidation of petroleum hydrocarbons in soil: 30% hydrogen peroxide was added to the soil after polarity adjustment in step 2 at a hydrogen peroxide: soil mass ratio of 5:100, and the soil was continuously oscillated at a speed of 170 r / min for 30 h on a cyclotron oscillator to complete the process of in situ regulation of soil polarity and Fenton's efficient direct oxidation of petroleum hydrocarbons in soil.

[0093] After the reaction, the polarity control strategy can directly oxidize and remove 4398.42 mg / kg of petroleum hydrocarbons, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 71.86 mg / g, as shown in Figure 5(a).

[0094] Comparative Example 1:

[0095] The method in Example 1 was used to oxidize soil petroleum hydrocarbons without adding soil polarity control liquid; the iron salt used was ferrous sulfate. The rotation speed of the cyclotron was 160 r / min, and the contact time between the soil and the ferrous sulfate solution was 40 min. Fenton directly oxidized soil petroleum hydrocarbons using 30% hydrogen peroxide at a concentration of 450 mmol / L.

[0096] (1) Take the same mass of distilled water as in Example 1 and add ferrous sulfate to ensure that the molar concentration of ferrous sulfate in the distilled water is 5.8 mmol / L.

[0097] (2) The solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:12 and mixed, and placed on a cyclotron at 160 r / min for 20 min to ensure that the soil was in full contact with the ferrous sulfate solution.

[0098] (3) Add 30% hydrogen peroxide to the container in step 2. Continue to oscillate on the cyclotron for 36 hours. This completes the non-polar regulated soil petroleum hydrocarbon oxidation process.

[0099] After the reaction is completed, 3785.65 mg / kg of petroleum hydrocarbons can be directly oxidized and removed, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 32.20 mg / g, as shown in Figure 5(b).

[0100] Comparative Example 2:

[0101] The method in Example 2 was used to oxidize soil petroleum hydrocarbons without adding soil polarity regulating liquid; the iron salt used was ferrous chloride. The rotation speed of the cyclotron was 165 r / min, and the contact time between the soil and the ferrous sulfate solution was 60 min. Fenton directly oxidized soil petroleum hydrocarbons using 35% hydrogen peroxide at a concentration of 450 mmol / L.

[0102] (1) Take the same mass of distilled water as in Example 1 and add ferrous sulfate to ensure that the molar concentration of ferrous sulfate in the distilled water is 7 mmol / L.

[0103] (2) The solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:10 and mixed, and placed on a cyclotron at 165 r / min for 60 min to ensure that the soil was in full contact with the ferrous sulfate solution.

[0104] (3) Add 35% hydrogen peroxide to the container in step 2. Continue to oscillate on the cyclotron for 32 hours. This completes the non-polar regulated soil petroleum hydrocarbon oxidation process.

[0105] After the reaction is completed, 3098.42 mg / kg of petroleum hydrocarbons can be directly oxidized and removed, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 33.75 mg / g, as shown in Figure 5(b).

[0106] Comparative Example 3:

[0107] The method in Example 3 was used to oxidize soil petroleum hydrocarbons without adding soil polarity control liquid; the iron salt used was ferrous sulfate. The rotation speed of the cyclotron was 180 r / min, and the contact time between the soil and the ferrous sulfate solution was 20 min. Fenton directly oxidized soil petroleum hydrocarbons using 35% hydrogen peroxide at a concentration of 600 mmol / L.

[0108] (1) Take the same mass of distilled water as in Example 1 and add ferrous sulfate to ensure that the molar concentration of ferrous sulfate in the distilled water is 3 mmol / L.

[0109] (2) The solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:11 and mixed, and placed on a cyclotron at 180 r / min for 20 min to ensure that the soil was in full contact with the ferrous sulfate solution.

[0110] (3) Add 35% hydrogen peroxide to the container in step 2. Continue to oscillate on the cyclotron for 24 hours. This completes the non-polar regulated soil petroleum hydrocarbon oxidation process.

[0111] After the reaction is completed, 2993.61 mg / kg of petroleum hydrocarbons can be directly oxidized and removed, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 24.45 mg / g, as shown in Figure 5(b).

[0112] Comparative Example 4:

[0113] The method in Example 4 was used to oxidize soil petroleum hydrocarbons without adding soil polarity control liquid; the iron salt used was ferrous sulfate. The rotation speed of the cyclotron was 175 r / min, and the contact time between the soil and the ferrous sulfate solution was 50 min. Fenton directly oxidized soil petroleum hydrocarbons using 35% hydrogen peroxide at a concentration of 600 mmol / L.

[0114] (1) Take the same mass of distilled water as in Example 1 and add ferrous sulfate to ensure that the molar concentration of ferrous sulfate in the distilled water is 6 mmol / L.

[0115] (2) The solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:14 and mixed, and placed on a cyclotron at 175 r / min for 50 min to ensure that the soil was in full contact with the ferrous sulfate solution.

[0116] (3) Add 30% hydrogen peroxide to the container in step 2. Continue to oscillate on the cyclotron for 28 hours. This completes the non-polar regulated soil petroleum hydrocarbon oxidation process.

[0117] After the reaction is completed, 2365.50 mg / kg of petroleum hydrocarbons can be directly oxidized and removed, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 19.32 mg / g, as shown in Figure 5(b).

[0118] Comparative Example 5:

[0119] The method in Example 5 was used to oxidize soil petroleum hydrocarbons without adding soil polarity control liquid; the iron salt used was ferrous oxalate. The rotation speed of the cyclotron was 170 r / min, and the contact time between the soil and the ferrous sulfate solution was 40 min. Fenton directly oxidized soil petroleum hydrocarbons using 30% hydrogen peroxide at a concentration of 300 mmol / L.

[0120] (1) Take the same mass of distilled water as in Example 1 and add ferrous sulfate to ensure that the molar concentration of ferrous sulfate in the distilled water is 8 mmol / L.

[0121] (2) The solution prepared in step 1 and the petroleum-contaminated soil were added into a container at a mass ratio of 1:15 for mixing, and placed on a cyclotron at 170 r / min for 40 min to ensure that the soil was in full contact with the ferrous sulfate solution.

[0122] (3) Add 30% hydrogen peroxide to the container in step 2. Continue to oscillate on the cyclotron for 30 hours. This completes the non-polar regulated soil petroleum hydrocarbon oxidation process.

[0123] After the reaction is completed, 2049.61 mg / kg of petroleum hydrocarbons can be directly oxidized and removed, and the amount of petroleum hydrocarbons that can be removed per unit mass of hydrogen peroxide is 33.49 mg / g, as shown in Figure 5(b).

[0124] The performance of removing petroleum hydrocarbons is illustrated below by comparing different embodiments of the present invention with comparative examples in Table 1.

[0125] Table 1. Comparison of petroleum hydrocarbon removal performance

[0126]

[0127]

[0128] Table 1 shows the amount of petroleum hydrocarbon oxidation and the amount of petroleum hydrocarbon removal per unit of hydrogen peroxide in the embodiments and comparative examples. The polarity regulation method is used to enhance the Fenton degradation of petroleum hydrocarbons in soil. It can be seen that the amount of petroleum hydrocarbon oxidation in the comparative example is 2049.61-3785.65 mg / kg, the amount of petroleum hydrocarbon oxidation per unit of hydrogen peroxide is 19.32-33.75 mg / g, and the amount of petroleum hydrocarbon oxidation in the embodiment of the present invention is 4398.42-6220.20 mg / kg, and the maximum amount of petroleum hydrocarbon that can be removed is 6220.20 mg / kg, which is 1.19 times higher than that of the unregulated group. The degradation amount is not less than 4398.42 mg / kg; the removal amount per unit of hydrogen peroxide is 37.97-71.86 mg / g, and the degradation amount is not less than 37.97 mg / g. Compared with the traditional Fenton method, the polarity regulation strategy has significantly improved the removal amount of petroleum hydrocarbons in soil and the removal amount of petroleum hydrocarbons in soil per unit of hydrogen peroxide.

[0129] In addition, the hydroxyl radicals (0.35 x 10 -2 au) can oxidize up to 1032.62 mg / kg of petroleum hydrocarbons. After soil conditioning, both hydrophilic functional groups and hydrophilic organic matter increase, thereby enhancing soil polarity. This will promote the transfer of hydroxyl radicals in the liquid phase to the solid phase to directly oxidize petroleum hydrocarbons in the soil. Therefore, an enhanced petroleum hydrocarbon oxidation effect is obtained. This technology is suitable for in-situ remediation of petroleum hydrocarbon-contaminated soil, overcomes the disadvantage that traditional Fenton technology is difficult to effectively transfer hydroxyl radicals, and significantly improves the Fenton oxidation capacity of petroleum hydrocarbons in the soil. Therefore, the present invention has great application potential for removing soil petroleum hydrocarbons and is worthy of promotion and application.

[0130] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A method for in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil by Fenton, characterized in that: The following steps are involved: Step 1, adding 40 to 60 parts of distilled water and 0.3 to 1.0 parts of iron salt to 3 to 6 parts of hydrophilic organic matter according to a mass ratio, mixing evenly, to obtain a soil polarity regulating solution; Step 2, mixing the soil polarity regulating solution with the petroleum contaminated soil in a mass ratio of 1:(10-15), and placing the mixture in a cyclotron to oscillate and regulate the polarity of the soil; Step 3, according to the mass ratio of hydrogen peroxide to soil of (5-18):100, hydrogen peroxide is added to the petroleum-contaminated soil after shaking control and continuously shaken, that is, the process of in-situ control of soil polarity Fenton direct oxidation of petroleum hydrocarbons in the soil is completed.

2. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The hydrophilic organic matter is chitosan, humic acid or fulvic acid.

3. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The iron salt is ferrous sulfate, ferrous chloride or ferrous oxalate.

4. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The total petroleum hydrocarbon content in high-oil soil in petroleum contaminated soil is 9.76g / kg, and the total petroleum hydrocarbon content in low-oil soil is 3.0g / kg.

5. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The rotation speed of the cyclotron is 160-180 r / min, and the time for the petroleum-contaminated soil to fully contact with the soil polarity regulating liquid is 20-60 min.

6. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The molar concentration of the iron salt is 3-8 mmol / L.

7. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The mass fraction of the hydrogen peroxide is 30% to 35%.

8. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: Add hydrogen peroxide to the shaken soil and shake it continuously for 24 to 36 hours.

9. The method of in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil according to claim 1, characterized in that: The degradation amount of alkanes in the soil by the polarity control group is no less than 4398.42 mg / kg; the degradation amount of petroleum hydrocarbons by unit hydrogen peroxide is no less than 37.97 mg / g.

10. A soil polarity regulating solution used in the method according to any one of claims 1 to 8, characterized in that: The invention comprises the following raw materials in the following mass ratio: 3-6 parts of hydrophilic organic matter, 0.3-1.0 parts of iron salt and 40-60 parts of distilled water.

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