Method for repairing chlorinated organic matter contaminated soil by low-temperature plasma coupled with iron-manganese oxide-biochar

Abstract

The application discloses a method for repairing chlorinated organic matter contaminated soil by low-temperature plasma coupled with iron-manganese oxide-biochar, which introduces biochar to improve the soil pore structure and effectively enrich pollutants, thereby shortening the mass transfer distance of active substances and overcoming the problem of mass transfer difficulty in dense soil environment; the cyclic ions on the surface of iron-manganese oxide are used to capture electrons to promote the hydrogenolysis dechlorination process, the proportion of iron-manganese composite components is accurately controlled, the oxygen vacancy defects are regulated by a metal binder, the storage and re-release of active oxygen species in the soil are realized, the conversion utilization rate of long-acting oxygen species is improved, and the in-situ degradation of pollutants is effectively promoted. The method can not only greatly improve the repair effect on the contaminated soil without secondary pollution, but also significantly improve the energy efficiency and long-acting repair, and realizes the efficient, low-consumption and green repair of the chlorinated organic matter contaminated soil.

Description

Technical Field

[0001] This invention relates to the field of organic contaminated soil treatment technology, specifically a method for remediating chlorinated organic contaminated soil using low-temperature plasma coupled with iron-manganese oxide-biochar. Background Technology

[0002] With the continuous advancement of industrialization, chlorinated organic pollutants have been widely used in various industries such as pesticides, pharmaceuticals, and dyes. However, these pollutants are highly toxic, difficult to degrade, and have strong bioaccumulation properties, allowing them to remain stable in soil for a long time, thus posing a significant threat to ecological security and human health.

[0003] Current remediation strategies for chlorinated organic polluted soils mainly include adsorption, chemical oxidation, microbial degradation, and a series of advanced oxidation technologies. However, these methods generally face problems in practical applications, such as limited remediation effects, long reaction cycles, high reagent costs, and potential secondary pollution. Against this backdrop, low-temperature plasma technology, as an emerging advanced oxidation technology, has gradually attracted widespread attention due to its ability to rapidly generate highly efficient and non-selectively degradable hydroxyl radicals for chlorinated organic pollutants. This technology demonstrates great application potential in the remediation of chlorinated organic polluted soils due to its ease of operation, high remediation efficiency, and ease of industrial scaling. However, when dealing with dense soil environments, low-temperature plasma technology also faces problems such as poor mass transfer of active species and low utilization rates, which not only limit degradation efficiency but also lead to additional energy consumption. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a green, efficient, and low-consumption device and treatment method for remediating chlorinated organic polluted soil, solving the problems of low treatment efficiency and poor degradation effect on deep soil in existing remediation methods.

[0005] Technical solution: The present invention provides a method for remediating chlorinated organic polluted soil by low-temperature plasma coupling of iron-manganese oxide-biochar, wherein the iron-manganese oxide-biochar is composed of biochar and iron oxide and manganese oxide loaded on the biochar by a metal ion binder; the iron-manganese oxide-biochar is mixed with the polluted soil to be treated, and the mixed soil is subjected to discharge treatment by low-temperature plasma, and the remediated soil is obtained after the treatment is completed.

[0006] In the above technical solution, iron-manganese oxide-biochar with strong adsorption capacity, persistent metal ion pairs, and abundant oxygen vacancies is designed and prepared specifically for dense soil environments. By coupling this composite material with a low-temperature plasma system, long-lived species generated by the discharge are converted in situ into hydroxyl radicals in the soil, achieving green and efficient remediation of chlorinated organic pollutants in soil.

[0007] Preferably, a dielectric barrier discharge low-temperature plasma reactor is selected, the main body of which is a quartz disc reactor (100mm in diameter). The high-voltage electrode is connected to the power supply, the low-voltage electrode is grounded, and the two sides of the reactor are respectively connected to the gas inlet and the gas outlet. The gas flow rate is regulated by a gas flow meter, and parameters such as real-time voltage, current and discharge waveform are recorded by an oscilloscope.

[0008] Furthermore, the raw materials for preparing iron-manganese oxide-biochar include an iron precursor, a manganese precursor, a metal ion binder, and a biochar precursor, wherein the iron precursor is ferric nitrate, the manganese precursor is manganese nitrate, the metal ion binder is sulfonated polystyrene resin or sulfonated polypropylene, and the biochar precursor is straw, rice husk, or coconut shell.

[0009] Preferably, the biochar preparation method involves removing impurities from biomass, washing, drying, and sieving it, and then pyrolyzing it in a tubular furnace to obtain biochar; wherein the biomass is rice husk, straw, or coconut shell.

[0010] Preferably, in the preparation of biomass, the calcination temperature in the tubular furnace is 500-700℃, and the calcination time is 3-5h.

[0011] Preferably, the mass ratio of iron:manganese:metal binder:biochar is 2:1:0.75:20-100, that is, the elemental mass ratio of iron to manganese is 2:1, the metal binder is 0.25% of the total mass of the metal elements, and the total metal component loading is 5-10% of the biochar. For example, taking 0.5g of iron as a baseline, the corresponding mass of manganese is 0.25g. Based on this, 2.16g of ferric nitrate and 0.81g of manganese nitrate are weighed in sequence. The total metal mass is 0.75g (0.5g + 0.25g), and then 0.1875g of metal binder and 7.5-15g of biochar are weighed in.

[0012] Preferably, the iron salt is ferric nitrate, the manganese salt is manganese nitrate, and the metal binder is sulfonated polystyrene resin or sulfonated polypropylene.

[0013] Furthermore, the preparation method of iron-manganese oxide-biochar involves mixing manganese salt, iron salt, and biochar, and then obtaining iron-manganese oxide-biochar via a sol-gel method. The sol-gel method involves mixing the metal precursor, metal binder, and biochar in deionized water, stirring in a water bath at 40-60℃ for 3-6 hours, filtering, washing, and drying, and then calcining it in a tube furnace at 500-700℃ for 4-6 hours.

[0014] Furthermore, the concentration of chlorinated organic matter is 10-500 mg / kg, and the dosage of iron-manganese oxide-biochar in the chlorinated organic matter contaminated soil to be treated is 1-50 mg / g.

[0015] Furthermore, the working gas of the low-temperature plasma reactor is one or more of air, nitrogen, and oxygen, with a gas flow rate of 20-100 ml / min.

[0016] Furthermore, the processing conditions of the low-temperature plasma reactor are an input voltage of 37.5-85V, a duty cycle of 40%-70%, and a processing time of 15-90min.

[0017] In a specific scheme, a method for remediating chlorinated organic polluted soil using low-temperature plasma-coupled biochar materials includes the following steps:

[0018] S1. Soil Pretreatment

[0019] After removing impurities from the chlorine-containing organic polluted soil, grinding it, and filtering it through a 100-mesh sieve, a soil sample to be treated was obtained.

[0020] S2. Iron-manganese oxide-biochar preparation

[0021] Common biomass is cleaned, washed, and dried before being pyrolyzed in a tube furnace to obtain biochar. Manganese salts, iron salts, and a metal binder are mixed with biochar in a specific ratio, and iron-manganese oxide-biochar is prepared via a sol-gel method.

[0022] S3. Preparation before degradation

[0023] After mixing iron-manganese oxide-biochar with chlorine-containing organic polluted soil, the mixture is spread evenly inside the low-temperature plasma reactor. The gas supply switch is turned on and the gas flow meter is adjusted to provide a stable atmosphere.

[0024] S4. Soil Treatment

[0025] By adjusting the input voltage, duty cycle, and pulse frequency using a pulse generator and voltage regulator, the high-voltage pulse power supply is turned on to discharge the contaminated soil.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: By adding iron and manganese oxide-biochar to soil contaminated with chlorine-containing organic pollutants, the present invention can effectively improve the pore structure of the contaminated soil, promote the rapid mass transfer of active substances in the soil, and directionally adsorb pollutants through hydrogen bonding and other mechanisms, thereby shortening the mass transfer distance of active substances and increasing the probability of contact between chlorine-containing organic pollutants and active substances in the soil.

[0027] This invention utilizes the iron / manganese cyclic ion pair mechanism loaded on the surface of biochar to promote the dechlorination process of hydrogen through long-term effective electron capture. Under the induction of a metal binder, the iron and manganese bimetallic compounds are compressed to form an oxygen vacancy lattice structure, which can convert the highly mass-transferring gaseous ozone generated by plasma discharge into more reactive oxygen species with stronger oxidizing power. This enables the in-situ degradation of chlorinated organic pollutants in soil, significantly improving the degradation efficiency of pollutants and the energy efficiency of the device. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the dielectric barrier discharge low-temperature plasma device of the present invention; in the figure: 1-high pressure gas cylinder, 2-gas flow meter, 3-disc-type dielectric barrier low-temperature plasma device, 4-voltage regulator, 5-high voltage power supply, 6-pulse generator, 7-oscilloscope.

[0029] Figure 2 This is a schematic diagram of the method for removing chlorine-containing organic pollutants using low-temperature plasma-coupled biochar material according to the present invention.

[0030] Figure 3 This is a performance comparison diagram of the low-temperature plasma coupled iron-manganese oxide-biochar and each individual component of the present invention.

[0031] Figure 4 This is a performance comparison diagram of iron-manganese oxide-biochar with different metal component ratios coupled by low-temperature plasma according to the present invention.

[0032] Figure 5 This is a performance comparison chart of iron-manganese oxide-biochar with different amounts of metal binder added in the low-temperature plasma coupling of the present invention.

[0033] Figure 6 This is a performance diagram of the low-temperature plasma coupled iron-manganese oxide-biochar remediation of chlorine-containing organic pollutant-contaminated soil according to the present invention. Detailed Implementation

[0034] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0035] This invention provides a method for remediating chlorinated organic polluted soil using low-temperature plasma coupled biochar materials. The specific method is as follows:

[0036] S1. Soil Pretreatment

[0037] After removing impurities from the chlorine-containing organic polluted soil, grinding it, and filtering it through a 100-mesh sieve, a soil sample to be treated was obtained.

[0038] S2. Iron-manganese oxide-biochar preparation

[0039] Common biomass is cleaned, washed, and dried before being pyrolyzed in a tube furnace to obtain biochar. Manganese salts, iron salts, and a metal binder are mixed with biochar in a specific ratio, and iron-manganese oxide-biochar is prepared via a sol-gel method.

[0040] S3. Preparation before degradation

[0041] After mixing iron-manganese oxide-biochar with chlorine-containing organic polluted soil, the mixture is spread evenly inside the low-temperature plasma reactor. The gas supply switch is turned on and the gas flow meter is adjusted to provide a stable atmosphere.

[0042] S4. Soil Treatment

[0043] By adjusting the input voltage, duty cycle, and pulse frequency using a pulse generator and voltage regulator, the high-voltage pulse power supply is turned on to discharge the contaminated soil.

[0044] Unless otherwise specified, the conditions used in each embodiment are as follows:

[0045] In step S1, the concentration of chlorinated organic matter is 10-500 mg / kg;

[0046] In step S2, the common biochar is rice husk, the iron salt is ferric nitrate, the manganese salt is manganese nitrate, and the metal binder is sulfonated polystyrene resin or sulfonated polypropylene.

[0047] In step S2, the calcination temperature of the rice husk tube furnace is 600℃ and the calcination time is 4h.

[0048] In step S2, the mass ratio of iron:manganese:metal binder:biochar is 2:1:0.75:20-100, where iron refers to the mass of iron element and manganese refers to the mass of manganese element.

[0049] In step S2, the synthesis step of the sol-gel method is to mix the metal precursor, metal binder and biochar in deionized water, stir in a water bath at 60°C for 4 hours, filter, wash and dry, and then place it in a tube furnace for calcination at 600°C for 4 hours.

[0050] In step S3, the dosage of iron-manganese oxide-biochar is 1-50 mg / g;

[0051] In step S3, the working gas can be air, nitrogen, oxygen, or a mixture thereof, and the gas flow rate is 20-100 ml / min.

[0052] In step S4, the input voltage is 37.5-85V, the duty cycle is 40%-70%, and the processing time is 15-90min.

[0053] The selected low-temperature plasma reactor, such as Figure 1As shown, the atmosphere required for discharge is provided by a high-pressure gas cylinder 1, and the gas flow rate is precisely adjusted by a gas flow meter 2. The main body of the reactor is a medium-barrier disc reactor 3 (100 mm in diameter). The energy required for the discharge to generate plasma is provided by a high-voltage power supply 5. The input power is adjusted by a voltage regulator 4 and a pulse generator 6. The real-time operating parameters of the device can be dynamically monitored by an oscilloscope 7.

[0054] like Figure 1 As shown, the dielectric barrier discharge cryogenic plasma device used in this embodiment of the invention has a main body of a quartz disc reactor (100mm in diameter). The high-voltage electrode is connected to a power supply, and the low-voltage electrode is grounded. An inlet and an outlet are connected to both sides of the reactor, respectively. The gas flow rate is regulated by a gas flow meter, and parameters such as real-time voltage, current, and discharge waveform are recorded using an oscilloscope. Specifically, the disc-shaped dielectric barrier cryogenic plasma device 3 is connected to a voltage regulator 4 and a gas flow meter 2. The gas flow meter 2 is connected to a high-pressure gas cylinder 1. The voltage regulator 4 is connected to a high-voltage power supply 5 and also to a pulse generator 6. The oscilloscope 7 is connected to the high-voltage power supply 5.

[0055] like Figure 2 As shown, gas molecules enter the reactor through the inlet. After power is switched on, under the influence of the electric field between the high-voltage electrode and the ground electrode, high-energy electrons collide with gas molecules inelastically, inducing their excitation and dissociation. Through free radical chain reactions, they form highly oxidizing reactive particles such as hydroxyl radicals (·OH), which rapidly act on the gas-solid interface, producing long-lived reactive substances such as gaseous ozone (O3). Ozone can rapidly migrate and transfer mass in the soil environment, contacting organic matter in deeper soil layers; however, due to its relatively weak reactivity, its contribution to pollutant degradation is small. The introduction of iron-manganese oxide-biochar improves the soil pore structure, which facilitates rapid mass transfer of reactive substances in the soil medium. Simultaneously, the circulating ion pairs on the surface of the iron-manganese oxide can capture electrons, promoting the dechlorination process of pollutants. Under the induction of the metal binder, the oxygen vacancy defects formed by the iron-manganese composite component can achieve the storage and release of oxygen species, converting O3 into more oxidizing ·OH. 1 O2 and O2 ·- This method rapidly targets and degrades chlorinated organic pollutants accumulated around the biochar material. This coupling approach not only improves the remediation efficacy of the device for chlorinated organic contaminated soil but also significantly enhances energy efficiency.

[0056] Example 1

[0057] This embodiment provides a method for remediating polychlorinated biphenyl (PCB) contaminated soil using low-temperature plasma coupling of iron-manganese oxide-biochar. Iron-manganese oxide-biochar (containing a metal binder), biochar, iron-biochar (containing a metal binder), and manganese-biochar (containing a metal binder) are prepared and mixed with the PCB-contaminated soil to be treated. The resulting mixed soil samples are placed in a low-temperature plasma reactor and subjected to discharge treatment to obtain the remediated soil.

[0058] Specifically, 300g of polychlorinated biphenyl (PCB) contaminated soil with a concentration of 500mg / kg was prepared in the laboratory. Rice husks were calcined at 600℃ for 4 hours to obtain biochar. Ferric nitrate, manganese nitrate, sulfonated polystyrene resin, and biochar were weighed according to the mass ratio of iron:manganese:sulfonated polystyrene resin:biochar = 2:1:0.75:50. The mixture was stirred in a water bath at 50℃ for 3 hours. After filtration, washing, and drying, it was placed in a tube furnace and calcined at 600℃ for 4 hours to obtain iron-manganese oxide-biochar. Biochar, iron-biochar, and manganese-biochar were prepared according to the single-component ratio, and added to the soil to be treated at a dosage of 10 mg / g. After being mixed evenly, the mixture was spread evenly in the plasma reactor. Air was introduced as the working gas at a flow rate of 30 mL / min. The input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz. The high-voltage power supply was started to discharge and generate active substances. The total discharge time was 60 minutes. 2 g samples were taken from the sampling port every 10 minutes. After extraction, the concentration of residual polychlorinated biphenyls in the soil samples was tested. The results are as follows: Figure 3 As shown.

[0059] After 60 minutes of discharge treatment, the low-temperature plasma device showed good remediation effect on polychlorinated biphenyl (PCB) contaminated soil, with a removal rate of 38%. However, due to mass transfer challenges in the soil medium, the degradation rate gradually slowed down with prolonged treatment time. Adding biochar to the soil optimized the soil pore structure, slightly improving the remediation effect of the low-temperature plasma, but the improvement was not significant. Adding a single metal component improved the remediation effect to some extent, with removal rates reaching 54.31% and 61.74% within 60 minutes, respectively. However, due to the lack of sustainable ion pairs, the metal component was easily deactivated, and the lack of oxygen vacancies resulted in low utilization of oxygen species such as ozone, thus the effectiveness and long-term sustainability of the coupling effect were insufficient. In contrast, iron-manganese oxide-biochar, with its reducing Mn... 2+ Fe 3+The ions and functional groups on the surface of biochar can effectively enrich pollutants and dechlorinate them via hydrogenation. Simultaneously, thanks to the multiple variable valence states of Mn, metal ion pairs can cycle through redox reactions, ensuring long-term catalytic effectiveness. Furthermore, under the induction of the metal binder, the oxygen vacancies formed by the mutual compression of different metal lattices can effectively convert ozone, thus significantly improving the remediation effect of low-temperature plasma on chlorinated organic contaminated soil. After 60 minutes of treatment, the removal rate of polychlorinated biphenyls in the soil reached 91.95%, demonstrating excellent coupled remediation effects.

[0060] Example 2

[0061] This embodiment provides a method for remediating polychlorinated biphenyl (PCB) contaminated soil using low-temperature plasma coupling of iron-manganese oxide-biochar. Iron-manganese oxide-biochar with different iron-manganese ratios is prepared and mixed with PCB-contaminated soil to be treated. The resulting mixed soil samples are placed in a low-temperature plasma reactor and subjected to discharge treatment to obtain remediated soil.

[0062] Specifically, 300g of polychlorinated biphenyl (PCB) contaminated soil at a concentration of 500mg / kg was prepared in the laboratory, and rice husks were calcined at 600℃ for 4h to obtain biochar. Metal precursors (ferric nitrate and manganese nitrate) were weighed according to different iron / manganese mass ratios, and sulfonated polystyrene resin with a total metal component of 0.25% by mass was added as a metal binder. This mixture was then mixed with 40 times the mass of the biochar in deionized water, stirred in a 50℃ water bath for 3h, filtered, washed, and dried, and then calcined in a tube furnace at 600℃ for 4h to obtain iron-manganese oxide-biochar with different iron-manganese ratios. The material was added to the soil to be treated at a dosage of 10 mg / g, mixed evenly, and then spread evenly in the plasma reactor. Air was introduced as the working gas at a flow rate of 30 mL / min. The input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz. The high-voltage power supply was started to discharge and generate active substances. The total discharge time was 60 minutes. 2 g samples were taken from the sampling port every 10 minutes. After extraction, the concentration of residual polychlorinated biphenyls in the soil samples was tested. The results are as follows: Figure 4 As shown.

[0063] As the iron / manganese ratio increases, the enhancing effect of iron-manganese oxide-biochar on the remediation of polychlorinated biphenyl (PCB) contaminated soil by low-temperature plasma devices shows a trend of first increasing and then decreasing. Specifically, the treatment efficiency of this coupled system reaches its optimal state when the iron to manganese mass ratio is 2:1. If the iron content is too low, the ozone conversion rate will be slowed down due to the lack of active sites; conversely, if the manganese content is insufficient, the iron / manganese ion pairs cannot function effectively and are prone to causing lattice distortion, thereby affecting the formation of oxygen vacancies and restricting the transfer and release rate of reactive oxygen species.

[0064] Example 3

[0065] This embodiment provides a method for remediating polychlorinated biphenyl (PCB) contaminated soil using low-temperature plasma coupling of iron-manganese oxide-biochar. Iron-manganese oxide-biochar with different amounts of metal binder is prepared and mixed with PCB-contaminated soil to be treated. The resulting mixed soil samples are placed in a low-temperature plasma reactor and subjected to discharge treatment to obtain remediated soil.

[0066] Specifically, 300g of polychlorinated biphenyl (PCB) contaminated soil at a concentration of 500mg / kg was prepared in the laboratory, and rice husks were calcined at 600℃ for 4 hours to obtain biochar. Ferric nitrate and manganese nitrate were weighed according to an iron / manganese mass ratio of 2:1, and sulfonated polystyrene resin with different mass fractions of total metal components (0, 0.1, 0.2, 0.25, 0.3, and 0.4% respectively) was added as a metal binder. This mixture was then mixed with 50 times the mass of the metal biochar in deionized water and stirred in a 50℃ water bath for 3 hours. After filtration, washing, and drying, the mixture was calcined in a tube furnace at 600℃ for 4 hours to obtain iron-manganese oxide-biochar with different amounts of metal binder. The material was added to the soil to be treated at a dosage of 10 mg / g, mixed evenly, and then spread evenly in the plasma reactor. Air was introduced as the working gas at a flow rate of 30 mL / min. The input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz. The high-voltage power supply was started to discharge and generate active substances. The total discharge time was 60 minutes. 2 g samples were taken from the sampling port every 10 minutes. After extraction, the concentration of residual polychlorinated biphenyls in the soil samples was tested. The results are as follows: Figure 5 As shown.

[0067] With increasing metal binder content, the enhancing effect of iron-manganese oxide-biochar on the remediation of PCB-contaminated soil by low-temperature plasma devices showed a trend of first increasing and then decreasing. Specifically, the treatment efficiency of this coupling system reached its optimal state when the sulfonated polystyrene resin content was 0.25 times the mass of the total metal elements. Too low a metal binder content led to lattice collapse and weakened interatomic bonding, thus limiting the transport and utilization efficiency of reactive oxygen species. Conversely, too high a metal binder content covered the metal active sites, reducing catalytic activity and shortening the lifespan of the iron-manganese oxide-biochar.

[0068] Example 4

[0069] This invention provides a method for the degradation of 2,4-dichlorophenol in soil by low-temperature plasma coupling of iron-manganese oxide-biochar. Iron-manganese oxide-biochar is prepared and mixed with 2,4-dichlorophenol-contaminated soil to be treated. The resulting mixed soil sample is placed in a low-temperature plasma reactor and subjected to discharge treatment to obtain remediated soil.

[0070] Specifically, this invention provides a method for remediating 2,4-dichlorophenol contaminated soil using a low-temperature plasma device coupled with biochar materials, achieving a degradation rate that meets the requirements. First, 300g of polychlorinated biphenyl (PCB) contaminated soil at a concentration of 500mg / kg was prepared in the laboratory, and rice husks were calcined at 600℃ for 4 hours to obtain biochar. Ferric nitrate and manganese nitrate were weighed at a 2:1 iron / manganese mass ratio, and sulfonated polystyrene resin (0.25% by mass of total metal component) was added as a metal binder. This mixture was then mixed with 50 times the mass of the metal biochar in deionized water and stirred in a 50℃ water bath for 3 hours. After filtration, washing, and drying, the mixture was calcined in a tube furnace at 600℃ for 4 hours to obtain iron-manganese oxide-biochar. The material was added to the soil to be treated at a dosage of 10 mg / g, mixed evenly, and then spread evenly in the plasma reactor. Air was introduced as the working gas at a flow rate of 30 mL / min. The input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz. The high-voltage power supply was started to discharge and generate active substances. The total discharge time was 60 minutes. 2 g samples were taken from the sampling port every 10 minutes. After extraction, the concentration of residual 2,4-dichlorophenol in the soil samples was tested. The degradation rate of 2,4-dichlorophenol-contaminated soil remediated by the low-temperature plasma device coupled with biochar material method is shown in the figure below. Figure 6 As shown, after 60 minutes of plasma treatment, the degradation rate of 500 mg / kg 2,4-dichlorophenol reached 95.05%.

[0071] Example 5

[0072] This invention provides a method for degrading chlorobenzene in soil using low-temperature plasma coupled biochar material. Iron-manganese oxide-biochar is prepared and mixed with chlorobenzene-contaminated soil to be treated. The resulting mixed soil sample is placed in a low-temperature plasma reactor and subjected to discharge treatment to obtain remediated soil.

[0073] Specifically, 300g of chlorobenzene-contaminated soil with a concentration of 500mg / kg and 300g of polychlorinated biphenyl-contaminated soil with a concentration of 500mg / kg were prepared in the laboratory. Rice husks were then calcined at 600℃ for 4 hours to obtain biochar. Ferric nitrate and manganese nitrate were weighed according to a 2:1 iron / manganese element mass ratio. Sulfonated polystyrene resin with a total metal component of 0.25% by mass was added as a metal binder. This mixture was then mixed with 50 times the mass of the metal biochar in deionized water and stirred in a 50℃ water bath for 3 hours. After filtration, washing, and drying, the mixture was calcined in a tube furnace at 600℃ for 4 hours to obtain iron-manganese oxide-biochar. The material was added to the soil to be treated at a dosage of 10 mg / g, mixed evenly, and then spread evenly in the plasma reactor. Air was introduced as the working gas at a flow rate of 30 mL / min. The input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz. The high-voltage power supply was started to discharge and generate active substances. The total discharge time was 60 minutes. 2 g samples were taken from the sampling port every 10 minutes. After extraction, the residual chlorobenzene concentration in the soil samples was tested. The degradation rate of chlorobenzene-contaminated soil remediated by the low-temperature plasma device coupled with biochar material method is as follows: Figure 6 As shown, after 60 minutes of plasma treatment, the degradation rate of chlorobenzene at 500 mg / kg reached 99.59%.

[0074] Example 6

[0075] This invention provides a method for degrading p-nitrochlorobenzene in soil using low-temperature plasma coupled biochar material. Iron-manganese oxide-biochar is prepared and mixed with p-nitrochlorobenzene-contaminated soil to be treated. The resulting mixed soil sample is placed in a low-temperature plasma reactor and subjected to discharge treatment to obtain remediated soil.

[0076] Specifically, first, 300g of soil contaminated with p-nitrochlorobenzene at a concentration of 500mg / kg and 300g of soil contaminated with polychlorinated biphenyls at a concentration of 500mg / kg were prepared in the laboratory. Rice husks were then calcined at 600℃ for 4 hours to obtain biochar. Ferric nitrate and manganese nitrate were weighed according to a 2:1 iron / manganese element mass ratio. Sulfonated polystyrene resin with a total metal component of 0.25% by mass was added as a metal binder. This mixture was then mixed with 50 times the mass of the metal biochar in deionized water and stirred in a 50℃ water bath for 3 hours. After filtration, washing, and drying, the mixture was calcined in a tube furnace at 600℃ for 4 hours to obtain iron-manganese oxide-biochar. The material was added to the soil to be treated at a dosage of 10 mg / g, mixed evenly, and then spread evenly in the plasma reactor. Air was introduced as the working gas at a flow rate of 30 mL / min. The input voltage was adjusted to 50 V, the duty cycle to 50%, and the pulse frequency to 200 Hz. The high-voltage power supply was started to discharge and generate active substances. The total discharge time was 60 minutes. 2 g samples were taken from the sampling port every 10 minutes. After extraction, the concentration of residual p-nitrochlorobenzene in the soil samples was tested. The degradation rate of p-nitrochlorobenzene-contaminated soil remediated by the low-temperature plasma device coupled with biochar material method is as follows: Figure 6 As shown, after 60 minutes of plasma treatment, the degradation rate of 500 mg / kg p-nitrochlorobenzene reached 88.71%.

Claims

1. A method for remediating chlorinated organic polluted soil using low-temperature plasma coupled with iron-manganese oxide-biochar, characterized in that, The iron-manganese oxide-biochar consists of biochar and iron oxide and manganese oxide loaded onto the biochar by a metal ion binder. The iron-manganese oxide-biochar is mixed with the contaminated soil to be treated, and the mixed soil is subjected to discharge treatment by low-temperature plasma. After the treatment, the remediated soil is obtained. The mass ratio of iron:manganese:metal binder:biochar is 2:1:0.75:20-100. The method for preparing the iron-manganese oxide-biochar is as follows: manganese nitrate, ferric nitrate, metal ion binder and biochar are weighed, mixed in deionized water, stirred in a water bath at 40-60℃ for 3-6 h, filtered, washed and dried, and then calcined in a tube furnace at 500-700℃ for 4-6 h. The metal ion binder is sulfonated polystyrene resin or sulfonated polypropylene.

2. The method for remediating chlorinated organic polluted soil using low-temperature plasma coupled with iron-manganese oxide-biochar as described in claim 1, characterized in that, Biochar precursors are straw, rice husks, or coconut shells.

3. The method for remediating chlorinated organic polluted soil using low-temperature plasma coupled with iron-manganese oxide-biochar as described in claim 1, characterized in that, The preparation method of biochar involves removing impurities, washing, drying and sieving the biochar precursor, and then pyrolyzing it in a tube furnace to obtain biochar.

4. The method for remediating chlorinated organic polluted soil using low-temperature plasma coupled with iron-manganese oxide-biochar as described in claim 3, characterized in that... In the preparation of biochar, the calcination temperature in the tube furnace is 500-700℃, and the calcination time is 3-5 h.

5. The method for remediating chlorinated organic polluted soil using low-temperature plasma coupled iron-manganese oxide-biochar as described in claim 1, characterized in that, The concentration of chlorinated organic matter is 10-500 mg / kg, and the dosage of iron-manganese oxide-biochar in the soil contaminated with chlorinated organic matter to be treated is 1-50 mg / g.

6. The method for remediating chlorinated organic polluted soil using low-temperature plasma coupled iron-manganese oxide-biochar as described in claim 1, characterized in that, The working gas of the low-temperature plasma reactor is one or more of the following gases: air, nitrogen, and oxygen, with a gas flow rate of 20-100 mL / min.

7. The method for remediating chlorinated organic polluted soil using low-temperature plasma coupled with iron-manganese oxide-biochar as described in claim 1, characterized in that, The processing conditions for the low-temperature plasma reactor are an input voltage of 37.5-85V, a duty cycle of 40%-70%, and a processing time of 15-90 min.

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