Remediation material for degrading organic contaminated soil by coupling manganese dioxide loaded biochar with chlorine dioxide and preparation method and remediation method of remediation material

Abstract

The invention relates to a remediation material for degrading organic contaminated soil by coupling manganese dioxide loaded biochar with chlorine dioxide and a preparation method and a remediation method of the remediation material, and belongs to the technical field of soil remediation, the remediation material comprises a biochar carrier and manganese dioxide nanoclusters loaded on the biochar carrier. Compared with the prior art, the manganese dioxide loaded biochar catalyst has excellent physical and chemical properties, the high specific surface area and the porous structure of the biochar provide a large number of active sites for MnO2 nanoparticles, and meanwhile, the adsorption performance of the biochar can effectively shorten the distance between the catalyst and pollutants and improve the reaction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a remediation material for degrading organically contaminated soil by coupling manganese dioxide-loaded biochar with chlorine dioxide, a preparation method thereof, and a remediation method thereof. Background Art

[0002] With the expansion of industrialization and rapid urbanization, soil contamination by organic pollutants is becoming increasingly serious. Organic pollutants like polycyclic aromatic hydrocarbons (PAHs) are strongly adsorbed to the soil surface due to their high hydrophobicity, altering its structure and properties, leading to a range of adverse effects, including reduced enzyme activity, altered microbial communities, and changes in vegetation. Effectively reducing and eliminating organic soil contamination is a pressing challenge in soil remediation.

[0003] Remediation technologies primarily encompass physics, chemistry, and biology. Physical remediation involves adsorption, which relies on materials such as activated carbon and biochar to absorb PAHs to reduce their concentration. Elution uses organic solvents and surfactants to elute PAHs to a liquid phase for subsequent treatment. Thermal decomposition involves heating to volatilize or decompose PAHs. Chemical remediation includes oxidation, which uses oxidants such as hydrogen peroxide, potassium permanganate, and persulfate to convert PAHs. Photocatalytic oxidation uses semiconductor photocatalysts to produce active free radicals under illumination to degrade PAHs. Chemical reduction targets halogenated PAHs for detoxification. Biological remediation involves microbial metabolic degradation of PAHs, and plant-derived pollution treatment through the synergistic use of root systems and rhizosphere microorganisms. However, adsorption methods face issues such as adsorption saturation, time-consuming microbial remediation, and the inactivation of photocatalytic oxidation catalysts. Therefore, oxidation remediation technology holds great potential for application in soil remediation.

[0004] Advanced chemical oxidation technologies are currently widely used to treat organically contaminated soils, with oxidants such as persulfate and hydrogen peroxide being widely used. However, these technologies have limitations, such as the relatively high price of persulfate and the potential for soil degradation caused by high concentrations of hydrogen peroxide, such as soil burns and microbial "vacuuming." Furthermore, organic pollutants are stubbornly adsorbed in aged soils, making them difficult to effectively degrade with oxidants. Even increasing the oxidant dosage does not significantly improve degradation.

[0005] Chinese patent CN118403614A invented a method for preparing a biochar in-situ loaded manganese oxide adsorbent. The biochar loaded manganese oxide in this patent mainly acts as an adsorbent by forming contact sites with pollutants on the surface of the biochar, but the selectivity is poor and it only efficiently adsorbs pollutants in a specific environment. Chinese patent CN116139852A discloses a tea biochar loaded manganese oxide composite material and its preparation method and application, but this technology is limited to the field of water purification environment technology and has defects such as high energy consumption and large equipment investment in the oxidant ozone preparation process, which makes it difficult to use in actual remediation projects. SUMMARY

[0006] The present application aims to overcome at least one of the above-mentioned defects in the prior art and provides a manganese dioxide loaded biochar coupled chlorine dioxide remediation material for degrading organic contaminated soil and a preparation method and a remediation method thereof.

[0007] The object of the present application can be achieved by the following technical solutions.

[0008] One of the objects of the present application is a manganese dioxide loaded biochar coupled chlorine dioxide remediation material for degrading organic contaminated soil, which comprises a biochar carrier and manganese dioxide nanoclusters loaded on the biochar carrier.

[0009] Further, the biochar carrier is camphor tree leaf biochar.

[0010] The second object of the present application is to provide a preparation method of the remediation material, which is the remediation material as described above, and the preparation method comprises the following steps.

[0011] S1, dissolving potassium permanganate and sodium acetate in water to obtain a mixed solution;

[0012] S2, uniformly mixing the mixed solution with a reducing agent, and then adding it to a biochar dispersion liquid, and performing suction filtration after sufficient water bath reaction, and then freeze-drying the suction filtration product to obtain manganese oxide loaded biochar nanoparticles, denoted as MnO / BC NPs;

[0013] S3, calcining the MnO / BC NPs to obtain manganese dioxide loaded biochar nanoclusters, denoted as MnO2 / BC NPs.

[0014] Further, the preparation method of the reducing agent is: crushing air-dried camphor tree leaves, mixing them with water, heating in a water bath, cooling to room temperature, and then performing suction filtration to obtain a camphor tree leaf extract, which is the reducing agent.

[0015] Further, the preparation method of the biochar dispersion liquid is: dispersing camphor tree leaf biochar in water to obtain the biochar dispersion liquid.

[0016] Further, in S3, the calcination temperature is at least 600 DEG C, and the calcination carrier gas condition is air.

[0017] Further, the mass ratio of the camphor tree leaf biochar to the potassium permanganate is (3-4):1.

[0018] The third object of the present application is a remediation method for organic contaminated soil, which uses the remediation material as described above,

[0019] The repair method comprises the following steps: uniformly mixing the organic contaminated soil, the repair material and the oxidant and reacting, adding a sodium thiosulfate solution to quench the reaction after the reaction is completed, so as to terminate the reaction, and obtaining the repaired soil after centrifugation.

[0020] Further, the mass ratio of the organic contaminated soil, the repair material and the oxidant is 100:(4-24):(1-6).

[0021] Further, the oxidant is chlorine dioxide, including one or more of liquid chlorine dioxide and solid chlorine dioxide.

[0022] Mechanism of action: The present application uses electron paramagnetic resonance (EPR) and other technologies to detect active oxygen species generated during the reaction process, and finds that using manganese dioxide loaded biochar nanoclusters as a catalyst can activate chlorine dioxide to produce chlorine oxygen radicals, hydroxyl radicals and superoxide radicals, and the hydroxyl radicals further oxidize the polycyclic aromatic hydrocarbons through hydroxylation and ring cleavage, and the chlorine oxygen radicals and superoxide radicals initiate free chain reactions by selectively reacting with electron-rich groups, so that the polycyclic aromatic hydrocarbon molecules are ultimately converted into small molecular compounds.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application provides a repair material for degrading organic contaminated soil by manganese dioxide loaded biochar coupled with chlorine dioxide, which is a catalyst of manganese dioxide loaded biochar and has excellent physical and chemical properties. The high specific surface area and porous structure of biochar provide a large number of active sites for MnO2 nanoparticles, and the adsorption performance of biochar can effectively shorten the distance between the catalyst and the pollutants, thereby improving the reaction efficiency.

[0025] (2) The present application provides a preparation method of the repair material, which is relatively simple, and the biochar is widely available and low in cost, and the MnO2 has low biological toxicity, which makes the preparation and use of the catalyst more economical and environmentally friendly.

[0026] (3) The present application provides a repair method for organic contaminated soil, and the synergistic effect of the repair material and chlorine dioxide can significantly improve the degradation efficiency of polycyclic aromatic hydrocarbons in the soil. Compared with traditional single repair technologies such as thermal desorption and soil leaching, the present application has the advantages of low energy consumption, short repair period and wide application range. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Degradation rate of PAHs in different reaction systems;

[0028] Figure 2Degradation rate of PAHs in the reaction system of the synthesized catalyst for different biochar;

[0029] Figure 3 Degradation rate of PAHs in the reaction system of the synthesized catalyst for different reducing agents;

[0030] Figure 4 Degradation rate of PAHs in the reaction system of different manganese oxide loaded biochar;

[0031] Figure 5 Degradation rate of PAHs in different reaction systems under acidic conditions;

[0032] Figure 6 DMPO and TEMPO capture signal diagram in the BC@MnO2 NPs / ClO2 reaction system DETAILED DESCRIPTION

[0033] The application will be described in detail below with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following examples.

[0034] The organic contaminated soil selected in the following examples and comparative examples is polycyclic aromatic hydrocarbon contaminated soil, which is obtained from a coking plant in Shenyang. The soil is dried in a fume hood, and stones and impurities are picked out. The soil is ground to 65 mesh, and then sieved (0.25 mm) and stored in a glass container for use.

[0035] Example 1

[0036] The embodiment provides a preparation method of a manganese dioxide loaded biochar coupled chlorine dioxide remediation material for degrading organic contaminated soil, and the method comprises the following steps:

[0037] S1. 10 g of camphor tree leaves are weighed, 250 ml of deionized water is added, and the mixture is heated in a 80℃ water bath for 1 h. The mixture is naturally cooled to room temperature and filtered. The filtrate is used as a camphor tree leaf extract.

[0038] S2. 3 g of camphor tree leaf biochar is dispersed in 25 ml of water to obtain a biochar solution.

[0039] S3. 1 g of KMnO4 and 5 g of sodium acetate are dissolved in 100 ml of deionized water to prepare a mixed solution.

[0040] S4, after the mixed solution was added into 200 ml of camphor tree leaf extract, the biochar solution was added and stirred in a 70°C water bath for 8 h. After cooling and centrifugation, the mixture was placed in a refrigerator for 24 h and freeze-dried for 48 h to obtain manganese oxide-loaded biochar nanoparticles, denoted as MnO / BC NPs;

[0041] S5, the prepared black solid MnO / BC NPs were uniformly placed in a quartz boat, which was placed in the center of a muffle furnace. The program of the muffle furnace was set to increase to 600°C at a rate of 5°C / min, and maintained at 600°C in an air atmosphere for 4 h to obtain manganese dioxide-loaded biochar nanoparticle clusters, denoted as MnO2 / BC NPs.

[0042] Example 2

[0043] The present embodiment provides a method for remediation of organic contaminated soil, and the specific operation is as follows:

[0044] 0.5 g of polycyclic aromatic hydrocarbon contaminated soil was taken in a reaction bottle, 5 mg of the remediation material prepared in Example 1 was added, and 10 ml of 1500 mg / L chlorine dioxide aqueous solution was mixed uniformly. The reaction system was placed in a constant temperature oscillator, and the speed was set to 180 rpm and the temperature was set to 25°C. The reaction time was controlled and the reaction was carried out. After the reaction was completed, 1 mL of 50 mM sodium thiosulfate solution was quickly added to the reaction system to quench the reaction and terminate the reaction. The reaction system was separated into solid and liquid by centrifugation at a speed of 3500 rpm for 20 min. The supernatant was discarded, and the solid part in the system was retained to obtain the remediated soil.

[0045] 5 mL of n-hexane and 5 mL of dichloromethane were added to the remediated soil, and the mixture was vortexed in a vortex instrument at a speed of 2500 rpm for 20 min. The extractant and the soil were mixed thoroughly, so that the pollutants in the remediated soil could be completely extracted by the extractant. The detection was carried out by gas chromatography-mass spectrometry.

[0046] The present embodiment also provides a control group, which is a contaminated soil without adding a catalyst, and the operation is carried out according to the above steps.

[0047] The results show that, thanks to the catalytic effect of the catalyst, the degradation effect of the catalyst-added group is better than that of the control group with only oxidant added. Under this concentration of oxidant, the degradation effect can be improved by 5%. If the same degradation effect is to be achieved, the concentration of oxidant needs to be increased. However, increasing the concentration of oxidant will further damage the organic matter and mineral structure in the soil. Therefore, the catalyst can optimize the amount of oxidant, i.e. reduce the concentration of oxidant while not reducing the degradation efficiency, and reduce the negative impact on the soil. As shown in the following table. Figure 1

[0048] Example 3 ​

[0049] The present embodiment is basically the same as embodiment 2, except that in the present embodiment, the catalyst material is prepared by replacing the camphor leaf biochar with cow dung biochar which also has a high specific surface area. The results show that the use of camphor leaves as a support to form a composite material does not cause void blockage, resulting in a decrease in specific surface area, and other problems, making the camphor leaf biochar as a manganese dioxide nanocluster carrier catalyst better at degrading polycyclic aromatic hydrocarbons in soil when coupled with chlorine dioxide, as shown in Figure 2 .

[0050] Embodiment 4

[0051] The present embodiment is basically the same as embodiment 1, except that in the present embodiment, the catalyst material is prepared by selecting the traditional chemical reagent hydrogen peroxide (H2O2) as the reducing agent. The results show that there is little difference in the degradation effect of polycyclic aromatic hydrocarbons in soil when compared with the catalyst synthesized using camphor leaf extract as a reducing agent coupled with chlorine dioxide, but plant extract is derived from natural plants, avoiding the secondary pollution that may be produced in traditional chemical synthesis methods, in line with the concept of green chemistry, so it is better to use green methods to prepare biochar loaded manganese dioxide nanoclusters. As shown in Figure 3 .

[0052] Embodiment 5

[0053] The present embodiment is basically the same as embodiment 1, except that in the present embodiment, the manganese oxide loaded biochar obtained under different calcination conditions is compared as a catalyst, and the results show that the high-temperature calcination under air atmosphere can optimize the pore structure of the biochar and form more oxygen-containing functional groups, which have better dispersibility and more active sites with manganese dioxide, so the degradation effect of the biochar loaded manganese dioxide nanoclusters obtained under the calcination condition of 600+N2+4h is not as good as that of the biochar loaded manganese dioxide nanoclusters obtained under the calcination condition of 600+Air+4h, and the degradation effect of the biochar loaded manganese dioxide nanoclusters obtained under the calcination condition of 280+N2+4h is not as good as that of the biochar loaded manganese dioxide nanoclusters obtained under the calcination condition of 600+Air+4h, so the biochar loaded manganese dioxide nanoclusters are the best catalyst. As shown in Figure 4 .

[0054] Embodiment 6

[0055] The present embodiment is basically the same as embodiment 1, except that in the present embodiment, the pH of the reaction system is adjusted to be slightly acidic, about 1-2. Since the acidic environment helps to form more surface functional groups on the surface of the biochar and the active sites on the surface of the manganese dioxide to better activate chlorine dioxide, generating more free radicals (such as sulfate radicals and hydroxyl radicals), the results show that the degradation effect is improved by 15% after adding the catalyst compared with the control group with only the oxidizing agent, as shown in Figure 5 .

[0056] Embodiment 7

[0057] The signal diagram of the hydroxyl radical and superoxide radical in the BC@MnO2 NP-activated ClO2 system in Example 2 was detected by an electron paramagnetic resonance spectrometer, as shown in Figure 6 , TEMPO and DMPO were used as the capture agents, and the EPR spectrum was determined by using a Bruker-emx-8 type x-band EPR spectrometer. The results show that the hydroxyl radical and superoxide radical exist in the BC@MnO2 NP-coupled ClO2 system, the hydroxyl radical and superoxide radical do not exist in the chlorine dioxide system alone, and the hydroxyl radical and superoxide radical help to enhance the oxidation activity of the oxidant, thereby improving the PAHs degradation efficiency.

[0058] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can modify or change the above disclosed technical content into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution of the present application, according to the technical essence of the present application, still belongs to the protection scope of the technical solution of the present application.

Claims

1. A remediation material for degrading organic contaminated soil by coupling manganese dioxide-loaded biochar with chlorine dioxide, characterized in that: The repair material comprises a biochar carrier and manganese dioxide nanoclusters loaded on the biochar carrier.

2. The remediation material for degrading organic contaminated soil by manganese dioxide-loaded biochar coupled with chlorine dioxide according to claim 1, characterized in that: The biochar carrier is camphor leaf biochar.

3. A method for preparing a repair material, characterized in that: The repair material is the repair material according to any one of claims 1 to 2, and the preparation method of the repair material comprises the following steps: S1. Dissolve potassium permanganate and sodium acetate in water to obtain a mixed solution; S2. The mixed solution and the reducing agent are mixed evenly, and then added to the biochar dispersion. After sufficient reaction in a water bath, the mixture is filtered, and the filtered product is freeze-dried to obtain biochar nanoparticles loaded with manganese oxide, which are recorded as MnO / BC NPs. S3. Calcinate MnO / BC NPs to obtain manganese dioxide-loaded biochar nanoclusters, which are recorded as MnO2 / BC NPs.

4. The method for preparing a repair material according to claim 3, characterized in that: The reducing agent is prepared by crushing air-dried camphor tree leaves and mixing them with water, heating them in a water bath, cooling them to room temperature, and then filtering them to obtain a camphor tree leaf extract, which is the reducing agent.

5. The method for preparing a repair material according to claim 3, characterized in that: The preparation method of the biochar dispersion liquid comprises the following steps: dispersing camphor leaf biochar in water to obtain the biochar dispersion liquid.

6. The method for preparing a repair material according to claim 3, characterized in that: In S3, the calcination temperature is at least 600° C., and the calcination carrier gas condition is air.

7. The method for preparing a repair material according to claim 5, characterized in that: The mass ratio of the camphor leaf biochar to the potassium permanganate is (3-4):

1.

8. A method for remediating organically contaminated soil, characterized in that: The repair method uses the repair material according to any one of claims 1-2, The remediation method comprises the following steps: uniformly mixing organically contaminated soil, remediation materials and an oxidant and reacting them; adding a sodium thiosulfate solution to quench the reaction after the reaction is completed to terminate the reaction; and obtaining the remediated soil after centrifugation.

9. The method for remediating organic contaminated soil according to claim 8, characterized in that: The mass ratio of the organic contaminated soil, the remediation material and the oxidant is 100:(4-24):(1-6).

10. The method for remediating organic contaminated soil according to claim 8, characterized in that: The oxidant is chlorine dioxide, including one or more of liquid chlorine dioxide and solid chlorine dioxide.

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