Remediation composition for petroleum hydrocarbon contaminated soil and its application

Abstract

The present invention provides a composition for remediating petroleum hydrocarbon-contaminated soil and its use. The composition comprises a peroxide, a persulfate, and a free radical initiator. By adding an initiator to a dual oxidant system comprising peroxide and persulfate, the use of catalysts and chelating agents can be avoided, resulting in a high degradation rate for petroleum hydrocarbons in the soil. It is believed that the addition of the initiator can stimulate the persulfate and calcium peroxide to generate active free radicals, generating SO4· ‑ They stimulate each other and work together to achieve the purpose of repairing soil contaminated by organic matter.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic matter contaminated soil remediation, and in particular relates to a remediation composition for petroleum hydrocarbon contaminated soil, a preparation method thereof, and an application thereof. Background Art

[0002] Organic pollutants and their harmful effects on human health and ecosystems are increasingly recognized. Furthermore, due to regional variations in soil, the complexity of ecosystems, and soil immobility, soil pollution is more complex and challenging to control than water or air pollution. Consequently, there is an urgent need to develop economically viable soil remediation technologies that are highly efficient at degrading recalcitrant organic pollutants.

[0003] Currently, there are many reports abroad on the degradation of organic pollutants in soil using single oxidants, such as peroxides, persulfates, and permanganates. These can achieve slow release of free radicals, high degradation efficiency, and long action times, and have good degradation effects on different organic pollutants. Among them, persulfate has attracted widespread attention due to its advantages such as a wide pH range, environmental friendliness, and long underground transmission distance. Due to its own limitations, single oxidant systems have limited ability to remove difficult-to-degrade pollutants. A mixture of hydrogen peroxide and sodium persulfate may have stronger oxidizing power. Reports on dual oxidants are relatively few, and the main reported dual oxidant system is hydrogen peroxide and persulfate. Although it has a good degradation effect on organic pollutants, it faces certain difficulties in practical application, such as the storage and transportation of hydrogen peroxide, the rapid release rate of hydrogen peroxide during organic matter degradation, and the short effective action time.

[0004] Calcium peroxide is reportedly a versatile, safe, solid inorganic peroxide that slowly releases hydrogen peroxide to produce ·OH in a humid environment. It is considered solid hydrogen peroxide and is well-suited for use in environmental remediation. The dual oxidant system, composed of persulfate and calcium peroxide, is less sensitive to environmental changes and exhibits high oxidative activity against a variety of organic pollutants. The synergistic effect between the two oxidants can also promote the oxidation of difficult-to-degrade organic pollutants, thereby improving degradation efficiency. This provides support for the development of technologies for remediating organically contaminated soils.

[0005] A soil remediation agent used in the prior art includes a surfactant, sodium persulfate, citric acid, ferrous salt, and alkaline peroxide. This technology uses surfactants to release adsorbed petroleum hydrocarbons that have strong binding forces with soil colloids, sodium persulfate to degrade petroleum hydrocarbons, and alkaline peroxide to adjust soil pH to degrade petroleum hydrocarbons in the soil. Although alkaline peroxide can avoid the soil acidification problem caused by sodium persulfate, the use of citric acid and ferrous salt increases the remediation cost, and citric acid complexes Fe2+ Activated sodium persulfate has a poor effect on the degradation of petroleum hydrocarbons in soil, with the degradation rate of petroleum hydrocarbons being less than 80%.

[0006] Another soil remediation agent used in the prior art consists of sodium persulfate, zero-valent iron, and calcium peroxide. By adding sodium persulfate to the system and heterogeneously activating it with zero-valent iron and calcium peroxide, two highly oxidizing radicals, sulfate and hydroxyl radicals, are simultaneously generated, expanding the range of pollutant degradation. While zero-valent iron is widely available and inexpensive, it is a solid particle and is less effective when used to activate sodium persulfate in solution. Consequently, this agent exhibits a low degradation rate for petroleum hydrocarbons (typically less than 85%) when used to remediate petroleum hydrocarbon-contaminated soil.

[0007] It can be seen from this that it is necessary to improve the existing oxidant system used for the remediation of organic contaminated soil and develop a petroleum hydrocarbon contaminated soil remediation method with high remediation efficiency, low remediation cost and environmental friendliness. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to overcome the problems of low degradation rate and high remediation cost of petroleum hydrocarbons in soil in the prior art, and to provide a remediation composition for petroleum hydrocarbon-contaminated soil and its application. The remediation composition of the present invention can increase the degradation rate of petroleum hydrocarbons in contaminated soil.

[0009] The objectives of the present invention are achieved through the following technical solutions.

[0010] In a first aspect, the present invention provides a remediation composition for petroleum hydrocarbon-contaminated soil, wherein the remediation composition comprises peroxide, persulfate, and a free radical initiator.

[0011] In the present invention, by adding an initiator to the dual oxidant system comprising peroxide and persulfate, the use of catalysts and chelating agents can be avoided, thereby improving the degradation rate of petroleum hydrocarbons in soil. Without wishing to be bound by theory, it is believed that the addition of the initiator can stimulate the persulfate and calcium peroxide to generate active free radicals, generating SO4· - They stimulate each other and work together to achieve the purpose of repairing soil contaminated by organic matter.

[0012] According to the repair composition provided by the present invention, the repair composition does not include a catalyst and / or a chelating agent.

[0013] According to the repair composition provided by the present invention, the peroxide is a solid inorganic peroxide. In some embodiments, the peroxide is calcium peroxide and / or magnesium peroxide.

[0014] According to the repair composition provided by the present invention, the persulfate is selected from at least one of sodium persulfate, potassium persulfate and ammonium persulfate. In some embodiments, the persulfate is sodium persulfate and / or potassium persulfate.

[0015] According to the repair composition provided by the present invention, the mass ratio of the peroxide to the persulfate is 1:2 to 8; in some embodiments, it is 1:3 to 6.

[0016] According to the repair composition provided by the present invention, the free radical initiator is a water-soluble azo initiator. Examples of water-soluble azo initiators suitable for use in the present invention include, but are not limited to, azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azobiscyanovaleric acid, and azobisisopropylimidazoline.

[0017] According to the repair composition provided by the present invention, the ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator can be 1:0.0005-0.01, preferably 1:0.001-0.005, and more preferably 1:0.001-0.004.

[0018] In a second aspect, the present invention provides use of the remediation composition in remediating petroleum hydrocarbon-contaminated soil.

[0019] According to the application provided by the present invention, the petroleum hydrocarbon content in the petroleum hydrocarbon contaminated soil is above 10,000 ppm.

[0020] In the present invention, there are no specific requirements for the size of the petroleum hydrocarbon-contaminated soil to be remediated. Generally, smaller soil particle size allows for more complete contact, thus facilitating remediation. However, reducing soil particle size generally increases treatment costs. In some embodiments, the particle size of the petroleum hydrocarbon-contaminated soil is 2 mm or less.

[0021] In the present invention, the petroleum hydrocarbons may be total petroleum hydrocarbons or any of their components. The present invention has no special requirements for this. The remediation composition of the present invention is applicable to soils contaminated by these petroleum hydrocarbons. In some embodiments, the petroleum hydrocarbons include C 10 ~C 40 Hydrocarbons, for example, diesel.

[0022] According to the application provided by the present invention, the application comprises the following steps:

[0023] S100, adding peroxide and a first portion of water to the petroleum hydrocarbon contaminated soil, and mixing to obtain a first mixture;

[0024] S200, mixing the initiator, the persulfate and the second portion of water and heating the mixture to obtain a second solution;

[0025] S300 , mixing the first mixture obtained in step S100 and the second solution obtained in step S200 .

[0026] According to the application provided by the present invention, in step S100, the amount of the peroxide used is 5g to 20g per kilogram of the petroleum hydrocarbon-contaminated soil; and / or the amount of the first portion of water used is 0.5kg to 2kg per kilogram of the petroleum hydrocarbon-contaminated soil.

[0027] According to the application provided by the present invention, in step S200, the mass ratio of the initiator to the second portion of water is 1:500-1500, preferably 1:800-1200, and more preferably 1:900-1100.

[0028] According to the application provided by the present invention, in step S200, based on 1000 parts by weight of the peroxide and the persulfate, the added amount of the initiator is 1 to 4 parts by weight.

[0029] According to the application provided by the present invention, the heating temperature in step S200 is 50° C. to 65° C. At such a temperature, the initiator is conducive to exciting the persulfate to generate active free radicals.

[0030] According to the application provided by the present invention, the mixing treatment in step S300 is performed for 1 to 12 hours, preferably 4 to 8 hours; and / or the mixing treatment is performed at room temperature.

[0031] According to the application provided by the present invention, step S300 further comprises: performing solid-liquid separation after the mixing process. In the present invention, any method known in the art can be used for solid-liquid separation, and the present invention is not particular thereto.

[0032] The above raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0033] Compared with the prior art, the present invention has at least the following advantages:

[0034] (1) In the repair composition of the present invention and its application, the use of catalysts and chelating agents can be avoided by adding an initiator, and the decomposition products of the initiator are non-toxic, which can reduce the repair cost and avoid the impact of the catalyst and chelating agent on the soil structure after repair.

[0035] (2) The repair method (application) provided by the present invention has a good repair effect. After the high-concentration petroleum hydrocarbon contaminated soil is repaired by this method, the removal rate of petroleum hydrocarbons can reach more than 90%, and the petroleum hydrocarbon content in the soil is lower than the second category of petroleum hydrocarbons (C 10 -C 40 )Soil pollution risk screening value: 4500mg / kg, which can meet the remediation requirements of petroleum hydrocarbon contaminated soil around operating enterprises such as petroleum and petrochemicals or abandoned plots.

[0036] (3) The addition of initiator can stimulate persulfate and calcium peroxide to generate active free radicals, and the generated SO4· - The OH group and the OH group interact and stimulate each other, working together to achieve the purpose of repairing organic contaminated soil. Using the remediation composition and remediation method (application) of the present invention, organic pollutants are completely degraded after remediation, and petroleum hydrocarbons can be degraded into small organic molecules, and even completely mineralized, without causing secondary pollution to the environment.

[0037] (4) The dual oxidant system not only improves the degradation efficiency of pollutants, but also converts refractory organic matter into easily degradable organic matter. In particular, solid inorganic peroxides can slowly release hydrogen peroxide during soil remediation, increasing the effective action time of the oxidant and fully exerting the oxidizing effect of the oxidant, thereby improving soil remediation efficiency and reducing remediation costs. Persulfate can generate free radicals over a wide pH range, making up for the low activity of peroxides under alkaline conditions. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0039] Preparation of contaminated soil samples:

[0040] (1) Collect soil from the 0-20 cm tillage layer, remove gravel and animal and plant debris from the soil, dry it at 200°C, and pass it through a 2 mm sieve to obtain uncontaminated soil for later use.

[0041] (2) A certain amount of diesel is dissolved in dichloromethane, and the prepared petroleum hydrocarbon / dichloromethane solution is added to the uncontaminated soil in the above step (1) under continuous stirring. After continuing to stir until uniform, the mixture is placed in a fume hood to allow the solvent to evaporate naturally, thereby obtaining petroleum hydrocarbon-contaminated soil.

[0042] Contaminated soils of different concentrations were prepared according to the different pollutant contents. The petroleum hydrocarbon content in the prepared contaminated soils was greater than 10,000 ppm, exceeding the second category of petroleum hydrocarbons (C10 -C 40 ) Soil pollution risk screening value: 4500mg / kg. Based on this, the following remediation tests were carried out.

[0043] Example 1

[0044] Weigh 10g of the prepared diesel-contaminated soil into a 50mL centrifuge tube. The petroleum hydrocarbon concentration in the soil was 10,000ppm. Add 10mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 30g of sodium persulfate in water to make an 80mL solution. Heat to 50°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0045] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0046] Example 2

[0047] Weigh 10g of the prepared diesel-contaminated soil into a 50mL centrifuge tube. The petroleum hydrocarbon concentration in the soil was 10,000ppm. Add 20mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 30g of sodium persulfate in water to make 80mL of the solution. Heat to 50°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0048] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0049] Example 3

[0050] Weigh 10g of the prepared diesel-contaminated soil into a 50mL centrifuge tube. The petroleum hydrocarbon concentration in the soil was 10,000ppm. Add 10mL of water and 0.05g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 15g of sodium persulfate in water to make 80mL of the solution. Heat to 50°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0051] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0052] Example 4

[0053] Weigh 10g of the prepared diesel-contaminated soil into a 50mL centrifuge tube. The petroleum hydrocarbon concentration in the soil was 10,000ppm. Add 10mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 50g of sodium persulfate in water to make an 80mL solution. Heat to 50°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0054] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0055] Example 5

[0056] Weigh 10g of the prepared diesel-contaminated soil into a 50mL centrifuge tube. The petroleum hydrocarbon concentration in the soil was 10,000ppm. Add 10mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 30g of sodium persulfate in water to make an 80mL solution. Heat to 50°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 8 hours.

[0057] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0058] Example 6

[0059] Weigh 10g of the prepared diesel-contaminated soil into a 50mL centrifuge tube. The petroleum hydrocarbon concentration in the soil was 15,000ppm. Add 10mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 30g of sodium persulfate in water to make an 80mL solution. Heat to 50°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0060] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0061] Example 7

[0062] Weigh 10g of laboratory-prepared diesel-contaminated soil (the petroleum hydrocarbon concentration in the soil was 10,000 ppm) into a 50mL centrifuge tube. Add 10mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.08g of azobisisobutylamidine hydrochloride and 30g of sodium persulfate in water to make an 80mL solution. Heat to 60°C. Add 0.8mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0063] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0064] Example 8

[0065] Weigh 10g of the prepared diesel-contaminated soil (the petroleum hydrocarbon concentration in the soil was 10,000 ppm) into a 50mL centrifuge tube. Add 10mL of water and 0.1g of calcium peroxide to the centrifuge tube and mix thoroughly in a vortex mixer. Dissolve 0.12g of azobisisobutylamidine hydrochloride and 30g of sodium persulfate in water to make a 120mL solution. Heat to 50°C. Add 1.2mL of this solution to the oxidant-soil mixture and place on a rotary shaker at room temperature for 4 hours.

[0066] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0067] Comparative Example 1

[0068] Weigh 10g of the prepared diesel-contaminated soil (the petroleum hydrocarbon concentration in the soil was 10,000 ppm) into a 50mL centrifuge tube. Add 10mL of deionized water to the centrifuge tube and mix thoroughly using a vortex mixer. Then, weigh 0.1g of calcium peroxide, 0.3g of sodium persulfate, 0.3861g of ferrous sulfate, and 0.2671g of citric acid into the centrifuge tube. Mix thoroughly using a vortex mixer and place on a rotary shaker at room temperature for 4 hours.

[0069] After the reaction, the aqueous and soil phases were separated by centrifugation, and the aqueous phase was discarded. The soil phase was freeze-dried and then subjected to pressurized solvent extraction using n-hexane using a rapid solvent extractor. The extract was concentrated to a fixed volume and analyzed for composition using gas chromatography. The results are listed in Table 1.

[0070] Table 1 Experimental results (ppm)

[0071] Example Initial pollutant concentration Residual pollutant concentration Degradation rate (%) 1 10000 820 91.8 2 10000 803 91.97 3 10000 985 90.15 4 10000 787 92.13 5 10000 811 91.89 6 15000 1350 91 7 10000 800 92 8 10000 790 92.1 Comparative Example 1 10000 2061 79.39

[0072] From the above results, it can be seen that the use of the remediation composition of the present invention, by adding a small amount of initiator, without using a catalyst and a chelating agent, the dual oxidant system composed of calcium peroxide and sodium persulfate has a good remediation effect on soil contaminated with high concentrations of petroleum hydrocarbons. The degradation rate of petroleum hydrocarbons in the soil is greater than 90%. The petroleum hydrocarbon content in the soil after remediation is lower than the second category of petroleum hydrocarbons (C 2 000) specified in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard (Trial)". 10 -C 40 ) soil pollution risk screening value, which has good application prospects.

[0073] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A composition for remediating soil contaminated by petroleum hydrocarbons, wherein: The repair composition includes peroxide, persulfate and a free radical initiator, the mass ratio of the peroxide to the persulfate is 1:2~8, and the ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator is 1:0.0005~0.01; wherein, the peroxide is calcium peroxide and / or magnesium peroxide, and the free radical initiator is a water-soluble azo initiator.

2. The repair composition according to claim 1, characterized in that The persulfate is selected from at least one of sodium persulfate, potassium persulfate and ammonium persulfate.

3. The repair composition according to claim 1, characterized in that The persulfate is sodium persulfate and / or potassium persulfate.

4. The repair composition according to any one of claims 1 to 3, characterized in that The mass ratio of the peroxide to the persulfate is 1:3-6.

5. The repair composition according to any one of claims 1 to 3, characterized in that The free radical initiator is at least one of azobisisobutylamidine hydrochloride, azobisisobutylimidazoline hydrochloride, azobisisobutylimidazoline sulfate, azobiscyanovaleric acid and azobisisopropylimidazoline.

6. The repair composition according to any one of claims 1 to 3, characterized in that The ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator is 1:0.001-0.

005.

7. The repair composition according to any one of claims 1 to 3, characterized in that The ratio of the mass of the peroxide and the persulfate to the mass of the free radical initiator is 1:0.001-0.

004.

8. Use of the remediation composition according to any one of claims 1 to 7 in remediating petroleum hydrocarbon contaminated soil.

9. The use according to claim 8, characterized in that The petroleum hydrocarbon content in the petroleum hydrocarbon contaminated soil is above 10,000 ppm; and / or The particle size of the petroleum hydrocarbon contaminated soil is less than 2 mm.

10. The use according to claim 8 or 9, characterized in that: The application comprises the following steps: S100, adding peroxide and a first portion of water to the petroleum hydrocarbon contaminated soil, and mixing to obtain a first mixture; S200, mixing the initiator, the persulfate and the second portion of water and heating the mixture to obtain a second solution; S300 , mixing the mixture obtained in step S100 with the second solution in step S200 .

11. The use according to claim 10, characterized in that In step S100, the amount of the peroxide used is 5 g to 20 g per kilogram of the petroleum hydrocarbon-contaminated soil; and / or the amount of the first portion of water used is 0.5 kg to 2 kg per kilogram of the petroleum hydrocarbon-contaminated soil; And / or, in step S200, the mass ratio of the initiator to the second portion of water is 1:500-1500.

12. The use according to claim 11, characterized in that In step S200, the mass ratio of the initiator to the second portion of water is 1:800-1200.

13. The use according to claim 11, characterized in that In step S200, the mass ratio of the initiator to the second portion of water is 1:900-1100.

14. The use according to claim 10, characterized in that The heating temperature in step S200 is 50°C to 65°C.

15. The use according to claim 10, characterized in that The mixing process in step S300 is performed for 1 to 12 hours; and / or the mixing process is performed at room temperature.

16. The use according to claim 10, characterized in that The mixing process in step S300 is performed for 4 to 8 hours.