A method for degrading soil organic pollutants, a biomass charcoal material and a preparation method thereof

Abstract

The application discloses a method for degrading soil organic pollutants, a biomass charcoal material and a preparation method. A self-supporting charcoal material with a high aspect ratio and capable of activating persulfate is partially inserted into soil containing organic pollutants and partially exposed to soil containing organic pollutants, and persulfate is added to the soil. Under illumination, the self-supporting charcoal material uses capillary action to adsorb soil organic pollutants to the part of the self-supporting charcoal material exposed to the illumination, and the self-supporting charcoal material activates the persulfate to degrade the adsorbed soil organic pollutants. The biomass charcoal with a high aspect ratio inherits the hydrophilicity of biomass and a natural vertical channel structure, and under the action of a thermal gradient and a concentration gradient, transports the soil organic pollutants to the inside of the biomass charcoal, and is mineralized under the oxidation of persulfate-derived radicals. In the case that the soil is not tilled and replaced, the purpose of degrading and removing the soil organic pollutants is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil organic pollution remediation, and relates to a method for degrading soil organic pollutants, a biomass charcoal material and a preparation method. BACKGROUND

[0002] In soil remediation technology, phytoremediation and bioremediation are used to reduce the concentration of soil pollutants by using the characteristics of absorption and enrichment of plants, animals and microorganisms. As a porous solid carbon material produced by pyrolysis of biomass, biochar has the characteristics of wide raw material sources, large specific surface area, rich functional groups, high cation exchange capacity and stable physicochemical properties, which can effectively reduce the migration and bioavailability of pollutants in soil and is widely used in soil remediation materials. Based on the activation of persulfate, advanced oxidation technology can produce strong oxidizing sulfate radicals through light, heating, metal ions and alkali, which can efficiently degrade water and soil pollutants. However, these activation methods are limited in soil application due to the need for specific conditions.

[0003] Patent CN113522355B discloses a nano composition formed by compounding biochar and potassium monopersulfate, which is used for degrading organic pollutants in wastewater or soil eluate. Patent CN113072164B discloses an active oxygen carbon for enhancing the efficiency of Fenton-like reaction in removing soil organic pollutants, which comprises biochar, calcium peroxide and silicate. Patent CN114540036A discloses an organic biochar remediation material prepared by impregnating solid waste such as kitchen waste with high organic matter content, residual sludge and biogas residue in a multi-metal ion solution and then calcining, which is used for soil-groundwater aniline pollution remediation. Patent CN112441659B discloses a multi-level mesoporous biochar material prepared by impregnating sugarcane residue with KOH and CaCl2 and then pyrolyzing in one step, which is used for activating persulfate to degrade organic pollutants in water.

[0004] Therefore, the existing biochar-based remediation materials are all in the form of powder applied to contaminated soil, which causes the adsorbed and fixed pollutants and their degradation products to remain in the soil. In the natural climate environment, the pollutants may still desorb and diffuse, causing recontamination. Unless soil replacement is performed, it is difficult to achieve the purpose of completely removing the pollutants. SUMMARY

[0005] The present application relates to the technical field of soil organic pollution remediation, and relates to a method for degrading soil organic pollutants, a biomass charcoal material and a preparation method.

[0006] The second object of the present application is to provide a self-supporting biochar material used in the above method.

[0007] A third objective of this invention is to provide a method for preparing the aforementioned self-supporting biochar material.

[0008] Technical solution: The method for degrading soil organic pollutants according to the present invention involves partially inserting a self-supporting biochar material with a high aspect ratio and capable of activating persulfate into soil containing organic pollutants, and partially exposing it to the outside of the soil containing organic pollutants. Persulfate is added to the soil. Under light, the self-supporting biochar adsorbs soil organic pollutants to the part of the self-supporting biochar material exposed to light through capillary action. The self-supporting biochar material activates the persulfate, thereby degrading the adsorbed soil organic pollutants.

[0009] The aspect ratio of the self-supporting biochar material is 0.3 to 100.

[0010] The self-supporting biochar material has a length of 30–1000 cm and a diameter of 10–100 cm.

[0011] The self-supporting biochar material is buried at a depth of 10–800 cm, and its exposed length in the soil is 20–200 cm.

[0012] The amount of persulfate added to the soil ranges from 1 to 500 mmol / m³. 3 .

[0013] The light intensity ranges from 0.5 to 1 solar intensity.

[0014] The self-supporting biochar material used in the above-mentioned method for degrading soil organic pollutants includes biochar with a high aspect ratio obtained by carbonizing biomass, and the biochar with a high aspect ratio is loaded with non-metallic heteroatoms and metal atoms for activating persulfate.

[0015] The biomass is bamboo and / or wood.

[0016] The above-mentioned method for preparing self-supporting biochar materials includes the following steps:

[0017] (1) Select biomass with a high aspect ratio, wash and dry it for later use;

[0018] (2) The biomass is immersed in a solution containing molten salt precursor and non-metallic heteroatom precursor, stirred thoroughly, and the solvent is evaporated to obtain the biomass precursor.

[0019] (3) The biomass precursor is calcined to obtain a self-supporting biochar material with a high aspect ratio containing non-metallic heteroatoms and metals.

[0020] In step (2), the molten salt precursor is a single-component or two-component alkali metal or alkaline earth metal halide, silicate, carbonate, nitrate or phosphate with a melting temperature of 200-600℃; the non-metallic heteroatom precursor is an organic compound containing B, N, S and P.

[0021] In step (2), the mass ratio of the biomass, molten salt precursor, and non-metallic heteroatom precursor is 1:0.01 to 10:0.01 to 1.

[0022] In step (2), the solvent of the solution is at least one of water, methanol, ethanol, ethylene glycol, glycerol, n-butanol, isobutanol, tert-butanol, 2-methoxyethanol, benzyl alcohol, or mannitol.

[0023] In step (2), the calcination temperature is 500-1000℃, the calcination time is 0.5-12h, and the heating rate is 1-20℃ / min.

[0024] In step (2), the calcination atmosphere is at least one of nitrogen, argon or ammonia.

[0025] Invention principle: Under light (or natural light), biochar undergoes photothermal conversion, and the surface temperature increases compared to the bulk temperature. Organic pollutants are adsorbed in the capillary channels of the self-supporting biochar and diffuse to the bulk phase and its surface under the temperature gradient. Under the action of free radicals generated by the activation of persulfate by metal atoms, the organic pollutants are degraded, thereby achieving the purpose of remediating polluted soil.

[0026] Beneficial Effects: Compared with existing technologies, this invention achieves the following significant effects: The self-supporting biochar of this invention contains non-metallic heteroatoms and metal atoms / nanoparticles, possessing the catalytic ability to activate persulfate; the black biochar has high photothermal conversion capacity, and inherits the hydrophilicity and natural vertical channel structure of biomass. Under the action of thermal and concentration gradients, organic pollutants in the soil can be transported into the biochar interior and mineralized under the oxidation of persulfate-derived free radicals. This achieves the purpose of degrading and removing organic pollutants from the soil without tilling or replacement. Detailed Implementation

[0027] The present invention will now be described in further detail.

[0028] Example 1

[0029] (1) Select a piece of wood that is 100cm long and 10cm in diameter, clean and dry it for later use;

[0030] (2) The wood was impregnated in an aqueous solution containing a mixed molten salt of LiCl / CoCl2 and melamine, with a mass ratio of wood:LiCl / CoCl2:melamine of 1:0.1:1. The impregnation was stirred thoroughly, and the solvent was evaporated to obtain the wood precursor.

[0031] (3) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 700°C at a heating rate of 5°C / min. It was calcined for 2 hours to obtain self-supporting doped biochar containing N and Co atoms.

[0032] (4) Bury the self-supporting biochar in soil containing organic pollutants to a depth of 80 cm, and add 100 mmol / m³ of water. 3 Persulfate degrades organic pollutants under light.

[0033] Example 2

[0034] (1) Select a piece of wood that is 80cm long and 15cm in diameter, clean and dry it for later use;

[0035] (2) The wood was impregnated in an aqueous solution containing a mixed molten salt of KCl / LiCl and melamine, with a mass ratio of wood:KCl / LiCl:thiourea of ​​1:3:1. The impregnation was stirred thoroughly, and the solvent was evaporated to obtain the wood precursor.

[0036] (3) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 800°C at a heating rate of 10°C / min. It was calcined for 1 hour to obtain self-supporting doped biochar containing N and S.

[0037] (4) Bury the self-supporting biochar in soil containing organic pollutants to a depth of 50 cm, and add 500 mmol / m³ of water. 3 Persulfate degrades organic pollutants under light.

[0038] Example 3

[0039] (1) Select bamboo with a length of 100cm and a diameter of 10cm, clean and dry it for later use;

[0040] (2) Bamboo was soaked in an aqueous solution containing KCl molten salt and sodium hypophosphite, with a mass ratio of bamboo:KCl:sodium hypophosphite of 1:1:0.1. The soaking was stirred thoroughly, and the solvent was evaporated to obtain wood precursor.

[0041] (3) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 900°C at a heating rate of 20°C / min. It was calcined for 2 hours to obtain self-supporting doped biochar containing P atoms.

[0042] (4) Bury the self-supporting biochar in soil containing organic pollutants to a depth of 80 cm, and add 300 mmol / m³ of water. 3 Persulfate degrades organic pollutants under light.

[0043] Example 4

[0044] (1) Select a piece of wood with a length of 1000cm and a diameter of 100cm, clean and dry it for later use;

[0045] (2) The wood was impregnated in an aqueous solution containing a mixed molten salt of LiCl / CoCl2 and melamine, with a mass ratio of wood:LiCl / CoCl2:melamine of 1:10:0.01. The impregnation was stirred thoroughly, and the solvent was evaporated to obtain the wood precursor.

[0046] (3) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 1000℃ at a heating rate of 20℃ / min. It was calcined for 0.5h to obtain self-supporting doped biochar containing N and Co atoms.

[0047] (4) Bury the self-supporting biochar in soil containing organic pollutants at a depth of 800 cm, with 200 cm protruding from the soil. Add 100 mmol / m 3 Persulfate degrades organic pollutants under light.

[0048] Example 4

[0049] (1) Select a piece of wood with a length of 500cm and a diameter of 50cm, clean and dry it for later use;

[0050] (2) The wood was impregnated in an aqueous solution containing a mixed molten salt of LiCl / CoCl2 and melamine, with a mass ratio of wood:LiCl / CoCl2:melamine of 1:0.01:1. The impregnation was stirred thoroughly, and the solvent was evaporated to obtain the wood precursor.

[0051] (3) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 500°C at a heating rate of 1°C / min. It was calcined for 12 hours to obtain self-supporting doped biochar containing N and Co atoms.

[0052] (4) Bury the self-supporting biochar in soil containing organic pollutants at a depth of 300cm, with 200cm protruding from the soil. Add 100mmol / m 3 Persulfate degrades organic pollutants under light.

[0053] Comparative Example 1

[0054] (1) Select a piece of wood that is 100cm long and 10cm in diameter, clean and dry it for later use;

[0055] (2) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 700°C at a heating rate of 5°C / min. It was calcined for 2 hours to obtain self-supporting biochar.

[0056] (3) Bury the self-supporting biochar in soil containing organic pollutants to a depth of 80 cm, and add 100 mmol / m³ of water. 3 Persulfate degrades organic pollutants under light.

[0057] Comparative Example 2

[0058] (1) Select bamboo with a length of 100cm and a diameter of 10cm, clean and dry it for later use;

[0059] (2) Bamboo is soaked in an aqueous solution containing molten KCl, with a mass ratio of bamboo to KCl of 1:1. The soaking is stirred thoroughly, and the solvent is evaporated to obtain wood precursor.

[0060] (3) The above wood precursor was transferred into a nitrogen atmosphere furnace and heated to 900°C at a heating rate of 20°C / min. It was calcined for 2 hours to obtain self-supporting biochar.

[0061] (4) Bury the self-supporting biochar in soil containing organic pollutants to a depth of 80 cm, and add 300 mmol / m³ of water. 3 Persulfate degrades organic pollutants under light.

[0062] Comparative Example 3

[0063] Based on Example 1, the difference from Example 1 is that the self-supporting doped biochar containing P atoms obtained in step (3) is ground and then incorporated into the soil.

[0064] Comparative Example 4

[0065] Based on Example 1, the difference is that the burial depth is 90cm.

[0066] Comparative Example 5

[0067] Based on Example 1, the difference is that the burial depth is 5cm.

[0068] The degradation effects of organic pollutants in the above embodiments and comparative examples were tested, and the data are shown in Table 1.

[0069] The testing method involved ultrasonic extraction to remove pollutants from the soil. Soil profile samples were collected using a 120cm long, 5cm diameter splitting sampler according to the "Technical Specification for Soil Environmental Monitoring" (HJ / T166-2004), at a depth of 10–800cm. Approximately 1kg of wet mixed sample was placed in a polyethylene self-sealing bag and thoroughly mixed. Simultaneously, approximately 5g of soil was taken using a sampler and injected into a polyethylene glass bottle containing a protective solution. The bottle was sealed immediately after sample collection. The sample was then thoroughly mixed with 1.0–2.0g of anhydrous sodium sulfate in a 100mL beaker. 50mL of a 1:1 mixture of dichloromethane and acetone was transferred to the beaker, and ultrasonic extraction was performed for 4 minutes under ice bath conditions, with a pulse interval of 4 seconds. The extraction was repeated three times. The extract from each extraction was transferred to a 500 mL flat-bottom flask and concentrated to 1-2 mL using a rotary evaporator at 39°C. Then, 10 mL of n-hexane was added, and the mixture was concentrated again to approximately 2 mL to obtain the extract for soil organic pollutants. The concentrated extract was then transferred to a chromatography column. First, it was eluted with 15 mL of a 1:1 mixture of dichloromethane and n-hexane (v / v), and the eluent was discarded. The column was then eluted again with 25-30 mL of the same dichloromethane and n-hexane mixture, and the eluent was collected in a 30 mL KD concentration flask. The eluent collected in the KD concentration flask was concentrated to 1 mL using a KD concentration apparatus before testing. The content of organic pollutants in the concentrated extract was determined using gas chromatography-mass spectrometry (GC-MS) (Agilent GC7890A-MSD5975C, USA). Chromatographic analysis conditions: CP2Sil 24CB column (30m×0.25mm×0.25μm); temperature program: 40℃, hold for 4 min, then increase from 40℃ to 270℃ at a rate of 10℃ / min, hold for 20 min; injection port temperature set to 260℃; He as carrier gas, flow rate 1.0 mL / min; splitless.

[0070] Table 1. Organic pollutant removal efficiency data for each embodiment and comparative example.

[0071]

Claims

1. A method for degrading soil organic pollutants, characterized in that, A self-supporting biochar material with a high aspect ratio and capable of activating persulfate is partially inserted into soil containing organic pollutants and partially exposed outside the soil containing organic pollutants. Persulfate is added to the soil. Under light, the self-supporting biochar uses capillary action to adsorb soil organic pollutants to the part of the self-supporting biochar material exposed to light. The self-supporting biochar material activates the persulfate and degrades the adsorbed soil organic pollutants. The aspect ratio of the self-supporting biochar material is 0.3~100; the length of the self-supporting biochar material is 30~1000cm; the diameter is 10~100cm; the burial depth of the self-supporting biochar material is 10~800cm; and the length exposed in the soil is 20~200cm. The self-supporting biochar material includes biochar with a high aspect ratio obtained by carbonizing biomass, and the biochar with a high aspect ratio is loaded with non-metallic heteroatoms and metal atoms for activating persulfate. The method for preparing the self-supporting biochar material includes the following steps: (1) Select biomass with a high aspect ratio, wash and dry it for later use; (2) The biomass is impregnated in a solution containing a molten salt precursor and a non-metallic heteroatom precursor, and the impregnation is stirred thoroughly. The solvent is then evaporated to obtain a biomass precursor. The molten salt precursor is a single-component or two-component alkali metal or alkaline earth metal halide, silicate, carbonate, nitrate or phosphate with a melting temperature of 200-600 °C. The non-metallic heteroatom precursor is an organic compound containing B, N, S and P. (3) The biomass precursor is calcined to obtain a self-supporting biochar material with a high aspect ratio containing non-metallic heteroatoms and metals.

2. The method for degrading soil organic pollutants according to claim 1, characterized in that, The addition amount of persulfate in soil is 1~500 mmol / m³. 3 .

3. The method for degrading soil organic pollutants according to claim 1, characterized in that, The light intensity is 0.5 to 1 solar intensity.

4. The method for degrading soil organic pollutants according to claim 1, characterized in that, The biomass is bamboo and / or wood.

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