A method for in-situ regulation of soil polarity and Fenton direct oxidation of petroleum hydrocarbons in soil

Abstract

This invention discloses a method for in-situ regulation of soil polarity to directly oxidize petroleum hydrocarbons in soil using Fenton oxidation. The method includes: thoroughly mixing hydrophilic organic matter with iron salts to prepare a soil polarity regulation solution; adding the prepared soil polarity regulation solution to petroleum-contaminated soil and agitating to regulate the polarity of the soil; then adding hydrogen peroxide and agitating continuously to efficiently and directly oxidize petroleum hydrocarbons in the soil. This invention enhances the Fenton degradation of petroleum hydrocarbons in soil, achieving maximum removal of petroleum hydrocarbons through polarity regulation; the enhanced soil polarity after regulation directly oxidizes petroleum hydrocarbons in the soil, significantly improving the Fenton oxidation capacity of petroleum hydrocarbons in the soil.

Description

Technical Field

[0001] This 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 and Fenton direct oxidation of petroleum hydrocarbons in soil. Background Technology

[0002] Petroleum hydrocarbons accidentally released into the environment during oil extraction, refining, transportation, and storage have resulted in significant soil contamination. This has become a major challenge in domestic environmental remediation. Fenton technology, with its ease of operation and rapid effectiveness, has attracted considerable attention from researchers in the field of chemical remediation. Among these technologies, in-situ chemical oxidation, with its rapid action and high site remediation potential, is one of the most widely used. Therefore, developing novel Fenton technologies suitable for in-situ remediation of petroleum hydrocarbon-contaminated soils is essential.

[0003] Currently, most Fenton oxidation technologies for petroleum hydrocarbons in soil rely on liquid-phase free radical reactions. However, petroleum hydrocarbons are bound to soil for extended periods, exhibiting strong hydrophobicity, which limits the reactivity of added Fenton reagents. Free radicals in the liquid phase have a short lifespan and are easily captured by soil organic matter, small molecules, and impurities, resulting in ineffective consumption. This explains the low efficiency of Fenton oxidation of petroleum hydrocarbons in soil. Similarly, this often necessitates the addition of large quantities of reagents to enhance the efficiency of soil remediation or the use of other synergistic technologies to strengthen the Fenton process. If free radicals could directly oxidize the petroleum hydrocarbons in the solid phase of the soil, it would significantly improve Fenton remediation efficiency and also save on reagent costs. Summary of the Invention

[0004] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a method for in-situ regulation of soil polarity and Fenton direct oxidation of petroleum hydrocarbons in soil. By introducing hydrophilic organic compounds with hydrophilic functional groups CH, CO, and C=O, the hydrophilicity and polarity of the soil are enhanced. This promotes the transfer of ·OH from the liquid phase to the solid phase for direct oxidation of petroleum hydrocarbons. It also improves the utilization rate of hydrogen peroxide, thereby achieving the goal of efficient Fenton direct oxidation of petroleum hydrocarbons in soil.

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

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

[0007] Step 1: Add 40-60 parts of distilled water and 0.3-1.0 parts of iron salt to 3-6 parts of hydrophilic organic matter by mass ratio, mix well, and obtain soil polarity regulating solution;

[0008] Step 2: Mix the soil polarity regulating solution with the petroleum-contaminated soil at a mass ratio of 1:(10-15), and place the mixture in a vortex shaker to regulate the soil polarity.

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

[0010] Step 3: Add hydrogen peroxide to the petroleum-contaminated soil after shaking and conditioning, according to the mass ratio of hydrogen peroxide to soil of (5-18):100, and shake continuously. This completes the process of in-situ conditioning of soil polarity and Fenton direct oxidation of petroleum hydrocarbons in the soil.

[0011] Preferably, the hydrophilic organic material 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 3–8 mmol / L.

[0013] As a preferred option, the total petroleum hydrocarbon content in high-oil soil was 9.76 g / kg, and the total petroleum hydrocarbon content in low-oil soil was 3.0 g / kg.

[0014] Preferably, the cyclone rotation speed is 160-180 r / min, and the contact time between the petroleum-contaminated soil and the soil polarity regulating solution is 20-60 min.

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

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

[0017] As a preferred method, hydrogen peroxide is added to the soil after it has been shaken and oscillated, and the soil is shaken continuously for 24–36 hours.

[0018] As a preferred embodiment, the polarity regulation group has a degradation amount of not less than 4398.42 mg / kg of alkanes in the soil; and a unit of hydrogen peroxide has a degradation amount of not less than 37.97 mg / g of petroleum hydrocarbons.

[0019] In another aspect, the present invention provides a soil polarity regulating solution used in the method, comprising the following raw materials in the following mass ratio: 3.0 to 6.0 parts of hydrophilic organic matter, 0.3 to 1.0 parts of iron salt, and 40 to 60 parts of distilled water.

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

[0021] 1. This invention uses hydrophilic organic matter, iron salt, and distilled water to prepare a soil polarity regulating solution. After being fully exposed to petroleum hydrocarbon-contaminated soil, the soil polarity is changed. The increased soil polarity can regulate hydroxyl radicals and guide hydroxyl radicals to efficiently and directly oxidize petroleum hydrocarbons in the soil solid phase.

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

[0023] 3. Increased soil polarity promotes the direct oxidation of petroleum hydrocarbons in the soil solid phase by hydroxyl radicals. This approach significantly enhances the utilization rate of free radicals and avoids losses during the migration and diffusion of free radicals in the traditional Fenton process. Most importantly, the direct generation of hydroxyl radicals in the solid phase increases the selectivity of the hydroxyl radicals participating in the reaction, allowing them to directly participate in subsequent oxidation reactions.

[0024] 4. This invention is used to increase the direct oxidation of petroleum hydrocarbons in soil. After polarity regulation, the Fenton oxidation capacity of petroleum hydrocarbons in soil can reach 4398.42-6220.20 mg / kg, which is higher than the oxidation capacity of petroleum hydrocarbons by traditional Fenton technology under the same conditions (2049.61-3785.65 mg / kg). After polarity regulation, the oxidation capacity of petroleum hydrocarbons by a unit of hydrogen peroxide is 37.97-71.86 mg / g, which is higher than the oxidation capacity of petroleum hydrocarbons by a unit of hydrogen peroxide by traditional Fenton technology under the same conditions (19.32-33.75 mg / g). Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

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

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

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

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

[0030] Figure 2(b) shows the three-dimensional fluorescence spectral analysis of soil organic matter distribution regulated by polarity;

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

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

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

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

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

[0036] Figure 3(c) shows the relationship between polarity control strategies and the traditional Fenton process on 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 process under similar petroleum hydrocarbon oxidation conditions;

[0038] Figure 4 The relationship between polarity and the amount of petroleum hydrocarbon oxidation;

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

[0040] Figure 5(b) shows the relationship between the amount of petroleum hydrocarbons oxidized and the amount of petroleum hydrocarbons oxidized per unit of hydrogen peroxide in a comparative example. Detailed Implementation

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

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

[0043] Step 1, Preparation of soil polarity regulating solution:

[0044] Mix 3.0–6.0 parts by mass of hydrophilic organic matter (chitosan, humic acid, or fulvic acid) with 40–60 parts by mass of distilled water until homogeneous. Then add 0.3–1.0 parts by mass of iron salt (ferrous sulfate, ferrous chloride, or ferrous oxalate) with a molar concentration of 3–8 mmol / L. Mix again until homogeneous to obtain the soil polarity regulating solution.

[0045] Step 2, regulate soil polarity:

[0046] The soil polarity regulating solution prepared in step 1 is added to the petroleum-contaminated soil at a mass ratio of 1:(10-15) and mixed in a container. The mixture is then placed in a vortex shaker and shaken at a speed of 160-180 r / min. The petroleum-contaminated soil and the soil polarity regulating solution are in full contact for 20-60 minutes to ensure that the soil and the soil polarity regulating solution are in full contact and to regulate the polarity of the soil by shaking.

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

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

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

[0050] Soil polarity can be regulated by the ratio of the integral area of ​​hydrophilic functional groups to humic acid-like substances. By adding hydrophilic organic matter, the hydrophilic functional groups (CH, CO, OH) on these substances can regulate soil polarity, thereby promoting the transfer of liquid-phase free radicals to the soil solid phase containing petroleum hydrocarbons, achieving efficient direct oxidation of petroleum hydrocarbons in the solid phase. Furthermore, these added hydrophilic organic substances are converted into humic acids, another type of organic matter commonly found in soil, during the reaction. This further improves soil hydrophilicity, enhances the transfer capacity of hydroxyl radicals, and increases the utilization rate of hydroxyl radicals. The final conversion of the added organic matter into humic acids already present in the soil also indicates that soil polarity regulation can avoid the hidden costs associated with subsequent pollution. The in-situ regulation characteristics can also reduce costs, ultimately achieving efficient degradation of petroleum hydrocarbons in the soil.

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

[0052] The decomposition mechanism of hydrogen peroxide was determined by the titanium sulfate colorimetric method using a UV-Vis spectrophotometer; residual petroleum hydrocarbons in the soil were determined by gas chromatography with a hydrogen ion flame detector, and the differences in petroleum hydrocarbon oxidation 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 spectroscopy; and the functional group characteristics of the soil were analyzed by Fourier transform infrared spectroscopy.

[0053] The efficient direct oxidation of petroleum hydrocarbons in soil by this invention can be seen from the following aspects:

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

[0055] The polarity modulation technique used in this invention enhances the peak intensity of typical hydrophilic functional groups in soil, including the stretching vibration peak of CO (1052 cm⁻¹). -1 (Integral intensity: 74.46), C=O stretching vibration peak (1620 cm⁻¹) -1 (Integral intensity: 14.89) and OH (3500cm) -1 (Integral intensity: 112.92), see Figure 1(a). In soils using the traditional Fenton technique, the related hydrophilic functional group peak intensities are lower. Among them, the stretching vibration peak of CO (1052 cm⁻¹) is the highest. -1 (Integral intensity: 51.55), C=O stretching vibration peak (1620 cm⁻¹) -1 (Integral intensity: 3.33) and OH (3500cm) -1 (Integral intensity: 42.64), see Figure 1(b). The change in hydrophilic functional groups is closely related to the amount of petroleum hydrocarbons oxidized. The amount of petroleum hydrocarbons oxidized in the polar regulation group with a larger hydrophilic functional group area is 1005.25 mg / kg higher than that in the traditional Fenton group, see Figure 1(c).

[0056] (2) Soil organic matter characteristics analysis

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

[0058] (3) The relationship between polar regulation strategy, changes in hydroxyl radicals and petroleum hydrocarbons

[0059] The changes in hydroxyl radicals over time under the polar regulation strategy were similar to those under the traditional Fenton method, as shown in Figures 3(a) and 3(b). Under similar total ·OH intensity conditions, the oxidation amounts of petroleum hydrocarbons in soil by H2O2 (30.73 au) and the polar regulation strategy (30.61 au) were 2143.51 mg / kg and 6220.20 mg / kg, respectively, under similar total ·OH intensity conditions, as shown in Figure 3(c). Furthermore, in experimental groups with similar petroleum hydrocarbon oxidation amounts, the ·OH concentration after polar regulation was only 5.97 x 10⁻⁶. -2 au can oxidize 3361.10 mg / kg of petroleum hydrocarbons; while the traditional Fenton technology requires a much larger amount of ·OH (43.35 x 10⁻⁶ mg / kg). -2 The 3393.61 mg / kg petroleum hydrocarbons were oxidized using au, as shown in Figure 3(d). This demonstrates the effectiveness of the polarity control strategy.

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

[0061] The increase in hydrophilic organic matter and functional groups was correlated with petroleum hydrocarbon oxidation. After regulation, soil polarity (η = 235.8, 450 mmol / L, TPH oxidation 6220.20 mg / kg) was greater than that of traditional Fenton (η = 181.87, 450 mmol / L, TPH oxidation 5214.95 mg / kg). This clearly indicates that TPH oxidation increased after soil polarity regulation. Furthermore, the difference in polarity (Δη = 53.97) was positively correlated with petroleum hydrocarbon oxidation (ΔTPH = 1005.50 mg / kg); η1 was correlated with petroleum hydrocarbon oxidation; and η2 was correlated with petroleum hydrocarbon oxidation. This suggests that polarity regulation promotes the efficient direct oxidation of petroleum hydrocarbons. (See...) Figure 4 .

[0062] The present invention will be further illustrated below through specific embodiments.

[0063] Example 1:

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

[0065] (1) Preparation of soil polarity regulation solution: Mix 5 parts of hydrophilic organic chitosan with 50 parts of distilled water according to the mass ratio, and then add 0.3 parts of ferrous sulfate to obtain the soil polarity regulation solution.

[0066] (2) Adjusting soil polarity: The soil polarity adjustment solution prepared in step 1 is added to the petroleum-contaminated soil at a mass ratio of 1:12 and mixed in a container. The mixture is placed in a vortex shaker and kept at 160 r / min for 40 min to ensure that the soil and the soil polarity adjustment solution are in full contact.

[0067] (3) Fenton efficient direct oxidation of soil petroleum hydrocarbons: Add 30% hydrogen peroxide to the soil after the polarity was regulated in step 2 at a hydrogen peroxide:soil mass ratio of 12:100, and continue to oscillate on a rotary shaker at a speed of 160r / min for 36h to complete the process of in-situ regulation of soil polarity and Fenton efficient direct oxidation of soil petroleum hydrocarbons.

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

[0069] Example 2:

[0070] The hydrophilic organic compound used was humic acid, and the ferric salt was ferrous chloride with a molar concentration of 7 mmol / L. High-oil soil with a total petroleum hydrocarbon content of 9.76 g / kg was used in the petroleum-contaminated soil treatment. The rotation speed of the cyclone oscillator was 165 r / min when adjusting soil polarity, and the contact time between the soil and the soil polarity adjustment solution was 60 min. For Fenton's efficient direct oxidation of petroleum hydrocarbons in the soil, 35% hydrogen peroxide at a concentration of 450 mmol / L was used.

[0071] (1) Preparation of soil polarity regulating solution: Mix 4 parts of hydrophilic organic humic acid with 60 parts of distilled water according to the mass ratio, and then add 0.4 parts of ferrous chloride to obtain the soil polarity regulating solution.

[0072] (2) Adjusting soil polarity: The soil polarity adjustment solution prepared in step 1 is added to the petroleum-contaminated soil at a mass ratio of 1:10 and mixed in a container. The mixture is placed in a vortex shaker and kept at 165 r / min for 60 min to ensure that the soil and the soil polarity adjustment solution are in full contact.

[0073] (3) Fenton efficient direct oxidation of soil petroleum hydrocarbons: Add 35% hydrogen peroxide to the soil after the polarity was regulated in step 2 at a hydrogen peroxide:soil mass ratio of 12:100, and continue to oscillate on a rotary shaker at a speed of 165r / min for 32h to complete the in-situ regulation of soil polarity and Fenton efficient direct oxidation of soil petroleum hydrocarbons.

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

[0075] Example 3:

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

[0077] (1) Preparation of soil polarity regulation solution: Mix 6 parts of hydrophilic organic chitosan with 40 parts of distilled water according to the mass ratio, and then add 0.7 parts of ferrous sulfate to obtain the soil polarity regulation solution.

[0078] (2) Adjusting soil polarity: The soil polarity adjustment solution prepared in step 1 is added to the petroleum-contaminated soil at a mass ratio of 1:14 and mixed in a container. The mixture is placed in a vortex shaker and kept at 180 r / min for 20 min to ensure that the soil and the soil polarity adjustment solution are in full contact.

[0079] (3) Fenton efficient direct oxidation of soil petroleum hydrocarbons: Add 35% hydrogen peroxide to the soil after the polarity was regulated in step 2 at a hydrogen peroxide:soil mass ratio of 18:100, and continue to oscillate on a rotary shaker at a speed of 180 r / min for 24 h to complete the in-situ regulation of soil polarity and Fenton efficient direct oxidation of soil petroleum hydrocarbons.

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

[0081] Example 4:

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

[0083] (1) Preparation of soil polarity regulating solution: Mix 3 parts of hydrophilic organic chitosan with 55 parts of distilled water according to the mass ratio, and then add 0.6 parts of ferrous sulfate to obtain the soil polarity regulating solution.

[0084] (2) Adjusting soil polarity: The soil polarity adjustment solution prepared in step 1 is added to the petroleum-contaminated soil at a mass ratio of 1:14 and mixed in a container. The mixture is placed in a vortex shaker and kept at 175 r / min for 50 min to ensure that the soil and the soil polarity adjustment solution are in full contact.

[0085] (3) Fenton efficient direct oxidation of soil petroleum hydrocarbons: Add 35% hydrogen peroxide to the soil after the polarity was regulated in step 2 at a mass ratio of 100:18, and continue to oscillate on a rotary shaker at a speed of 175 r / min for 28 h to complete the process of in-situ regulation of soil polarity and Fenton efficient direct oxidation of soil petroleum hydrocarbons.

[0086] (3) Fenton efficient direct oxidation of soil petroleum hydrocarbons: Add 35% hydrogen peroxide to the soil after the polarity was regulated in step 2 at a hydrogen peroxide:soil mass ratio of 18:100, and continue to oscillate on a rotary shaker at a speed of 175r / min for 28h to complete the in-situ regulation of soil polarity and Fenton efficient direct oxidation of soil petroleum hydrocarbons.

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

[0088] Example 5:

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

[0090] (1) Preparation of soil polarity regulation solution: Mix 3 parts of hydrophilic organic humic acid with 45 parts of distilled water according to the mass ratio, and then add 1.0 part of ferrous oxalate to obtain the soil polarity regulation solution.

[0091] (2) Adjusting soil polarity: The soil polarity adjustment solution prepared in step 1 is added to the petroleum-contaminated soil at a mass ratio of 1:15 and mixed in a container. The mixture is placed in a vortex shaker and kept at 170 r / min for 40 min to ensure that the soil and the soil polarity adjustment solution are in full contact.

[0092] (3) Fenton efficient direct oxidation of soil petroleum hydrocarbons: Add 30% hydrogen peroxide to the soil after the polarity was regulated in step 2 at a hydrogen peroxide:soil mass ratio of 5:100, and continue to oscillate on a rotary shaker at a speed of 170r / min for 30h to complete the process of in-situ regulation of soil polarity and Fenton efficient direct oxidation of soil petroleum hydrocarbons.

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

[0094] Comparative Example 1:

[0095] The method described in Example 1 was used for soil petroleum hydrocarbon oxidation without the addition of soil polarity control solution; ferrous sulfate was used as the iron salt. 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 direct oxidation of soil petroleum hydrocarbons was performed 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) Add the solution prepared in step 1 and the petroleum-contaminated soil to a container at a mass ratio of 1:12 and mix them. Place the container in a vortex shaker and maintain the mixture at 160 r / min for 20 min to ensure that the soil and ferrous sulfate solution are in full contact.

[0098] (3) Add 30% hydrogen peroxide to the container from step 2. Continue shaking on a gyroscope for 36 hours. This completes the non-polar controlled soil petroleum hydrocarbon oxidation process.

[0099] After the reaction, 3785.65 mg / kg of petroleum hydrocarbons can be directly oxidized and removed. The amount of petroleum hydrocarbons 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 described in Example 2 was used for soil petroleum hydrocarbon oxidation without the addition of soil polarity control solution; ferrous chloride was used as the iron salt. 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 direct oxidation of soil petroleum hydrocarbons was performed 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) Add the solution prepared in step 1 and the petroleum-contaminated soil to a container at a mass ratio of 1:10 and mix them. Place the container in a vortex shaker and maintain the mixture at 165 r / min for 60 min to ensure that the soil and ferrous sulfate solution are in full contact.

[0104] (3) Add 35% hydrogen peroxide to the container from step 2. Continue shaking on a gyroscope for 32 hours. This completes the non-polar controlled soil petroleum hydrocarbon oxidation process.

[0105] After the reaction, 3098.42 mg / kg of petroleum hydrocarbons can be directly oxidized and removed. The amount of petroleum hydrocarbons 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 described in Example 3 was used for soil petroleum hydrocarbon oxidation without the addition of soil polarity control solution; ferrous sulfate was used as the iron salt. 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 direct oxidation of soil petroleum hydrocarbons was performed 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) Add the solution prepared in step 1 and the petroleum-contaminated soil to a container at a mass ratio of 1:11 and mix them. Place the container in a vortex shaker and maintain the mixture at 180 r / min for 20 min to ensure that the soil and ferrous sulfate solution are in full contact.

[0110] (3) Add 35% hydrogen peroxide to the container from step 2. Continue shaking on a gyroscope for 24 hours. This completes the non-polar controlled soil petroleum hydrocarbon oxidation process.

[0111] After the reaction, 2993.61 mg / kg of petroleum hydrocarbons can be directly oxidized and removed. The amount of petroleum hydrocarbons 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 described in Example 4 was used for soil petroleum hydrocarbon oxidation without the addition of soil polarity control solution; ferrous sulfate was used as the iron salt. 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 direct oxidation of soil petroleum hydrocarbons was performed 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) Add the solution prepared in step 1 and the petroleum-contaminated soil to a container at a mass ratio of 1:14 and mix them. Place the container in a vortex shaker and maintain the mixture at 175 r / min for 50 min to ensure that the soil and ferrous sulfate solution are in full contact.

[0116] (3) Add 30% hydrogen peroxide to the container from step 2. Continue shaking on a gyroscope for 28 hours. This completes the non-polar controlled soil petroleum hydrocarbon oxidation process.

[0117] After the reaction, 2365.50 mg / kg of petroleum hydrocarbons can be directly oxidized and removed. The amount of petroleum hydrocarbons 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 described in Example 5 was used for soil petroleum hydrocarbon oxidation without the addition of soil polarity control solution; 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 direct oxidation of soil petroleum hydrocarbons was performed 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) Add the solution prepared in step 1 to the petroleum contaminated soil at a mass ratio of 1:15 and mix them in a container. Place the container in a vortex shaker and maintain the mixture at 170 r / min for 40 min to ensure that the soil and ferrous sulfate solution are in full contact.

[0122] (3) Add 30% hydrogen peroxide to the container from step 2. Continue shaking on a gyroscope for 30 hours. This completes the non-polar controlled soil petroleum hydrocarbon oxidation process.

[0123] After the reaction, 2049.61 mg / kg of petroleum hydrocarbons can be directly oxidized and removed. The amount of petroleum hydrocarbons 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 petroleum hydrocarbon oxidation and petroleum hydrocarbon removal per unit of hydrogen peroxide in the examples and comparative examples. By enhancing the Fenton degradation of petroleum hydrocarbons in soil through polarity regulation, it can be seen that the petroleum hydrocarbon oxidation in the comparative examples ranged from 2049.61 to 3785.65 mg / kg, and the petroleum hydrocarbon oxidation per unit of hydrogen peroxide ranged from 19.32 to 33.75 mg / g. In the examples of this invention, the petroleum hydrocarbon oxidation ranged from 4398.42 to 6220.20 mg / kg, with a maximum removal of 6220.20 mg / kg, which is 1.19 times higher than the unregulated group. The degradation amount was not less than 4398.42 mg / kg; the removal amount per unit of hydrogen peroxide ranged from 37.97 to 71.86 mg / g, and the degradation amount was not less than 37.97 mg / g. The polarity regulation strategy significantly improved the removal amount of petroleum hydrocarbons in soil and the removal amount per unit of hydrogen peroxide compared to the traditional Fenton method.

[0129] Furthermore, hydroxyl radicals (0.35 x 10⁻⁶) that enter the solid phase after polarity regulation -2 The maximum oxidant concentration of petroleum hydrocarbons (Au) is 1032.62 mg / kg. After soil conditioning, both hydrophilic functional groups and hydrophilic organic matter increase, thereby enhancing soil polarity. This promotes the transfer of hydroxyl radicals from the liquid phase to the solid phase for direct oxidation of petroleum hydrocarbons in the soil. Therefore, an enhanced petroleum hydrocarbon oxidation effect is achieved. This technology is suitable for in-situ remediation of petroleum hydrocarbon-contaminated soil, overcoming the shortcomings of traditional Fenton technology in effectively transferring hydroxyl radicals and significantly improving the Fenton oxidation capacity of petroleum hydrocarbons in the soil. Therefore, this invention has great potential for removing petroleum hydrocarbons from soil and is worthy of widespread application.

[0130] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for in-situ regulating the polarity of Fenton's direct oxidation of petroleum hydrocarbons in soil, characterized by, The method comprises the following steps: Step 1, adding 40-60 parts of distilled water and 0.3-1.0 parts of iron salt into 3-6 parts of hydrophilic organic matter according to the mass ratio, and mixing uniformly to obtain a soil polarity regulating solution; The hydrophilic organic matter is humic acid or fulvic acid; Step 2, mixing the soil polarity regulating solution with the petroleum-contaminated soil according to the mass ratio of 1:(10-15) and placing in a gyratory shaker to oscillate and regulate the polarity of the soil; The gyratory oscillation speed is 160-180 r / min, and the petroleum-contaminated soil is fully contacted with the soil polarity regulating solution for 20-60 min; Step 3, adding hydrogen peroxide into the oscillation-regulated petroleum-contaminated soil according to the mass ratio of (5-18):100, and continuously oscillating, so as to complete the process of in-situ regulating soil polarity and Fenton direct oxidation of petroleum hydrocarbon in the soil.

2. The method of in-situ regulating the soil polarity Fenton direct oxidation of petroleum hydrocarbons in soil according to claim 1, characterized in that, The iron salt is ferrous sulfate, ferrous chloride or ferrous oxalate.

3. The method of in-situ regulating soil polarity Fenton direct oxidation of petroleum hydrocarbons in soil according to claim 1, characterized in that, 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.

4. The method of in-situ modulating the soil polarity Fenton direct oxidation of petroleum hydrocarbons in soil according to claim 1, wherein, The molar concentration of the iron salt is 3-8 mmol / L.

5. The method of in-situ modulating the soil polarity Fenton-like direct oxidation of petroleum hydrocarbons in soil according to claim 1, wherein, The mass fraction of the hydrogen peroxide is 30%-35%.

6. The method of in-situ regulating the soil polarity Fenton direct oxidation of petroleum hydrocarbons in soil according to claim 1, characterized in that, The hydrogen peroxide is added into the oscillation-regulated soil, and continuously oscillated for 24-36 h.

7. The method of in-situ regulating the soil polarity Fenton direct oxidation of petroleum hydrocarbons in soil according to claim 1, characterized in that, The degradation amount of the alkane in the soil in the polarity regulating group is not less than 4398.42 mg / kg; and the degradation amount of the petroleum hydrocarbon per unit of hydrogen peroxide is not less than 37.97 mg / g.

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