Preparation and dynamic characterization method and application of a biochar-based phenanthrene removal in soil

Abstract

The present application belongs to the technical field of pollutant interface behavior characterization, and specifically discloses a preparation and dynamic characterization method and application of a biochar-based material for removing phenanthrene in soil. The method first selects biomass raw materials, pretreats and limits oxygen pyrolysis to obtain biochar, and then introduces one or more of metal active components, mineral components and organic functional components to obtain biochar-based composite materials with porous structure and interface activity. Then, the composite materials are added to the phenanthrene contaminated soil to construct a multi-medium system of composite material-soil particles-pore water-microbial community, and soil samples, pore water samples, material interface samples and microbial samples are collected according to the preset time gradient. Combined with phenanthrene content analysis, pore structure characterization, surface functional group characterization, micro-morphology and element distribution characterization, wettability characterization and microbial response analysis, the migration, adsorption, fixation, synergistic degradation and re-release trend of phenanthrene on the micro-interface are dynamically characterized.

Description

Technical Field

[0001] This invention relates to the fields of soil pollution remediation, preparation of environmental functional materials and characterization of pollutant interface behavior, specifically to a method and application for the preparation and dynamic characterization of biochar-based removal of phenanthrene from soil. Background Technology

[0002] Soil is a vital component of ecosystems, playing a crucial protective role in ecological processes such as water cycling, climate regulation, and nutrient cycling. It prevents soil erosion and water loss, reduces soil pollution, and protects biodiversity and ecological balance. Phenanthrene is a typical tricyclic polycyclic aromatic hydrocarbon (PAH) pollutant, widely found in soils affected by coking, oil refining, chemical, and transportation emissions. Due to its strong hydrophobicity and high environmental persistence, it easily accumulates in organic matter, mineral particles, and pore structures after entering the soil, influencing its migration and transformation behavior through complex interfacial interactions. Existing remediation studies on phenanthrene-contaminated soils primarily use removal rates or endpoint residues as evaluation criteria, lacking a systematic characterization of the dynamic migration and interfacial coupling of pollutants among material surfaces, soil particles, pore water, and microbial communities during the remediation process.

[0003] Biochar, with its advantages of wide availability, relatively simple preparation, rich pore structure, tunable surface functional groups, and good environmental compatibility, has become an important candidate material for the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil. Existing research has shown that biochar can participate in the removal of PAH pollutants through mechanisms such as hydrophobic partitioning, π-π interactions, pore filling, surface complexation, and electron transfer. However, single biochar still suffers from limitations in practical applications, including limited active sites, insufficient structural stability, and weak selectivity for specific pollutants. To improve its ability to remove phenanthrene, it is usually necessary to introduce metal oxides, mineral materials, humic components, or other functional components to modify the surface structure and interfacial properties of biochar, thus constructing biochar-based composite materials.

[0004] The existing technologies have the following main shortcomings: First, the analysis of material preparation and application mechanisms is relatively separate, making it difficult to establish a systematic correlation between "material structure, interface properties, and repair effect"; Second, most studies focus on static endpoint analysis and lack continuous dynamic characterization of phenanthrene migration from the soil solid phase to the material surface, diffusion in pores, fixation by interfacial active sites, and further microbial co-transformation; Third, existing characterization methods are mostly single-dimensional, making it difficult to achieve synergistic integration of multi-source information such as pollutant concentration, surface functional groups, pore structure, micro-area elemental distribution, wettability, and microbial behavior.

[0005] Therefore, developing a complete set of methods that take into account both the preparation of biochar-based composite materials and the dynamic characterization of micro-interface behavior is of great significance for constructing efficient and stable repair materials, revealing the key interface control steps in the phenanthrene removal process, and improving the targeting of process optimization and engineering applications. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for the preparation and dynamic characterization of phenanthrene in soil based on biochar. This method can not only prepare biochar-based composite materials with good interfacial activity, pore structure and surface functional characteristics, but also construct a multi-media coupling system of composite material-soil-pore water-microorganisms. It can dynamically identify and determine the micro-interfacial behaviors of phenanthrene during the remediation process, such as migration, adsorption, fixation, transformation, synergistic degradation and re-release. This provides technical support for the screening of biochar-based composite materials, optimization of phenanthrene-contaminated soil remediation processes and risk assessment of polycyclic aromatic hydrocarbon-contaminated soil.

[0007] To achieve the aforementioned objective, the technical solution of the present invention is implemented as follows: a method for preparing a biochar-based composite material for removing phenanthrene from soil and a method for dynamically characterizing its micro-interface behavior, comprising: S1, Preparation of biochar-based composite materials Biomass raw materials are selected, and after pretreatment by washing, drying and crushing, they are pyrolyzed under oxygen-limited conditions to obtain basic biochar. On this basis, one or more of the following can be introduced by impregnation, co-precipitation, hydrothermal method, ball milling, in-situ loading method, ultrasonic-assisted method or combination thereof to form a biochar-based composite material with target pore structure, surface functional groups, interfacial reactivity and adsorption and fixation capacity. The preparation steps are consistent with the process shown in the attached figure, and both include biomass raw material pretreatment, oxygen-limited pyrolysis, and composite modification.

[0008] Furthermore, the biomass raw material is one or more of the following: straw, sawdust, rice husks, fruit shells, sludge, and livestock and poultry manure.

[0009] Furthermore, the oxygen-limited pyrolysis temperature is 400–700°C, and the pyrolysis time is 1–4 h, in order to obtain basic biochar with a certain specific surface area, pore structure, and surface active sites.

[0010] Furthermore, the active metal component is one or more of the oxides, hydroxides, or salts of iron, manganese, calcium, and magnesium; the mineral component is one or more of bentonite, kaolin, zeolite, hydroxyapatite, attapulgite, and montmorillonite; and the organic functional component is one or more of humic acid, humate, or oxygen- or nitrogen-containing organic modifiers. By introducing these components individually or synergistically, the surface polarity, porosity, interfacial complexing ability, wettability, and adsorption and fixation capacity of the composite material can be controlled.

[0011] Furthermore, the composite modification method is preferably one or more of the following: impregnation, co-precipitation, hydrothermal method, ball milling, in-situ loading, and ultrasonic-assisted method. Different modification methods can distribute the active components on the surface of biochar, inside the pores, or at the surface-pore composite interface, thereby forming biochar-based composite materials with different micro-region structures, elemental distribution states, and surface chemical characteristics.

[0012] S2, Construction of the interaction system of phytotoxic soil The prepared biochar-based composite material was added to phenanthrene-contaminated soil at a set ratio. The moisture content, temperature, aeration status and incubation time were adjusted to construct a multi-media interaction system for removing phenanthrene from the soil using the composite material. The multi-media interaction system includes at least a biochar-based composite material phase, a soil solid phase, a soil pore water phase and a microbial interaction phase. Phenanthrene undergoes dynamic processes such as migration, distribution, adsorption, desorption, fixation, transformation and re-release between the various media and their interfaces.

[0013] The technical roadmap in the attached figure also shows the process of time-series characterization and mechanism analysis after the composite material is added to contaminated soil in the Philippines.

[0014] Furthermore, the initial concentration of the phenanthrene-contaminated soil is 50–500 mg / kg, the amount of biochar-based composite material added is 1%–5% of the soil mass, the culture temperature of the multi-media interaction system is 25–30℃, the soil moisture content is 50%–70% of the maximum water holding capacity, and the culture time is 7–84 days.

[0015] To ensure system stability and comparability of interfacial processes, the aeration status, soil turning frequency, and dark culture conditions in the culture container can be controlled according to experimental requirements to reduce interference from non-target factors on phenanthrene migration and transformation behavior.

[0016] Furthermore, during the remediation and cultivation process, biochar-based composite materials can remove and stabilize phenanthrene in the soil through pore filling, surface adsorption, π-π interactions, hydrogen bonding, electrostatic interactions, surface complexation, mineral synergistic fixation, and microbial synergistic degradation.

[0017] S3, Timing Sampling According to the preset time nodes, whole soil samples, pore water samples, material surface samples, interface micro-region samples, and microbial samples were collected to obtain the temporal information of the whole soil at different stages, which was used to reveal the dynamic laws of changes in phenanthrene content, interface parameters, and microbial responses during the remediation process.

[0018] The temporal sampling is used to reflect the changes in the repair effect over time, and also to establish the evolutionary trajectory of phenanthrene migration and fixation between multi-media interfaces.

[0019] The attached figures clearly show the time points, including 0 days, 1 day, 3 days, 7 days, 14 days, 21 days, and 28 days, and conduct evolution analysis of phenanthrene content and key interface parameters at different time points.

[0020] Furthermore, the time gradient includes at least four time points selected from 0 d, 1 d, 3 d, 7 d, 14 d, 21 d, and 28 d.

[0021] Furthermore, in order to detect the remediation effect and subsequent stabilization behavior, the remediation time can be extended to 84 days or 86 days in the later stages to obtain information on changes in phenanthrene residue levels, interface stability, and re-release potential in the mid-to-late stages.

[0022] Furthermore, the collected whole soil samples are used to analyze the total amount of phenanthrene, soil properties, and overall remediation effect; pore water samples are used to characterize the migration and availability of phenanthrene in the liquid phase; material surface samples and interface micro-region samples are used to analyze the functional groups, pore structure, elemental distribution, and micro-region morphology evolution of composite material surfaces; and microbial samples are used to analyze the changes in microbial community structure and activity during the remediation process.

[0023] S4, Dynamic Representation of Micro-interface Behavior The migration, adsorption, immobilization, synergistic degradation, and re-release processes of phenanthrene in the multi-media interface of composite materials, soil, pore water, and microorganisms were dynamically characterized using chromatographic analysis, surface chemical analysis, pore structure analysis, micro-region structure analysis, elemental distribution analysis, wettability analysis, and microbial behavior analysis.

[0024] This step not only focuses on the endpoint removal rate, but also on the dynamic changes in the physicochemical properties of the interface, micro-region morphology, surface active sites, and microbial responses at different time points, thereby achieving full-process tracking of the remediation process.

[0025] The attached technical roadmap further details the specific content, including phenanthrene content analysis, pore structure analysis, functional group analysis, micro-area morphology and elemental distribution analysis, wettability analysis, and microbial behavior analysis.

[0026] Furthermore, the pollutant concentration is determined using high-performance liquid chromatography, gas chromatography, or gas chromatography-mass spectrometry to determine the phenanthrene content in soil, pore water, or extract.

[0027] Furthermore, the surface chemical analysis employs Fourier transform infrared spectroscopy, Raman spectroscopy, or X-ray photoelectron spectroscopy to analyze the types of functional groups, changes in chemical bonds, surface element valence states, and functional group participation mechanisms on the composite material and its interface after interaction.

[0028] Furthermore, the pore structure analysis employs specific surface area analysis and pore size distribution analysis to characterize the pore volume, specific surface area, micropore-mesopore distribution of the composite material and their changes before and after repair.

[0029] Furthermore, the micro-region structure analysis employs scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, and laser confocal microscopy to analyze the material surface morphology, interface roughness, local microstructure, and elemental distribution at the micro-region interface.

[0030] Furthermore, the wettability analysis employs contact angle measurement to characterize the hydrophilic / hydrophobic properties of the material surface and changes in interfacial wetting behavior, thereby assisting in determining the distribution and adsorption characteristics of phenanthrene on the material surface.

[0031] Furthermore, the microbial behavior analysis employs high-throughput sequencing, phospholipid fatty acid analysis, enzyme activity assay, catalase activity assay, dehydrogenase activity assay, fluorescence staining, or extracellular polymer analysis to characterize the microbial community structure, abundance changes, metabolic activity, interfacial attachment behavior, and extracellular polymer secretion characteristics.

[0032] By combining the above-mentioned multi-source characterization methods, the adsorption and fixation of phenanthrene, interfacial transformation and biosynergistic effects of composite materials can be characterized from multiple dimensions such as phenanthrene content decay, pore structure change, functional group evolution, element migration, wettability adjustment and microbial response.

[0033] S5. Dynamic Fitting and Mechanism Determination Based on time-series data, key parameters were extracted using adsorption kinetics models, diffusion models, and interface stabilization evaluation models. The migration pathways, adsorption and fixation degree, interfacial transformation behavior, and re-release risk of phenanthrene were analyzed to determine the mechanism of action of biochar-based composite materials on phenanthrene.

[0034] Kinetic analysis is applicable not only to phenanthrene concentration variation data, but also to time series variation data of pore structure parameters, surface functional group characteristic parameters, wettability parameters, elemental distribution parameters, and microbial behavior parameters, in order to establish the correlation between phenanthrene removal process and interface evolution process.

[0035] The attached figures show that the following models can be used for fitting analysis: pseudo-first-order kinetic model, pseudo-second-order kinetic model, Elovich model, intraparticle diffusion model, and Fick diffusion model.

[0036] Furthermore, the kinetic fitting includes one or more of the following: pseudo-first-order kinetic model, pseudo-second-order kinetic model, Elovich model, intraparticle diffusion model, and Fick diffusion model.

[0037] Furthermore, based on the fitting results, one or more of the following can be calculated: interfacial adsorption rate constant, apparent desorption coefficient, interfacial diffusion coefficient, interfacial stabilization index, and re-release risk factor.

[0038] Furthermore, by comparing the changes in key parameters of different materials, different modified components, different addition ratios, and different cultivation stages, it can be determined whether the dominant controlling step of phenanthrene in the system is rapid surface adsorption, pore diffusion control, interfacial synergistic fixation, microbial-promoted degradation, or late-stage rebalancing release.

[0039] By combining the changes in phenanthrene content and the evolution of key interface parameters at different time points shown in the attached figures, we can further reveal the phased changes in the sources of phenanthrene removal contribution and the micro-interface control mechanism during the early, middle, and late stages of remediation.

[0040] The beneficial effects of this invention are reflected in: (1) The method provided by the present invention provides a method for preparing biochar-based composite materials, which clarifies the source of raw materials, pyrolysis conditions and composite modification path. After the composite material is prepared, a system for the action of phenanthrene-contaminated soil is constructed and the dynamic characterization of micro-interface behavior is carried out. This realizes the integrated design of material construction and application mechanism analysis. Furthermore, the application of biochar can increase the content of nutrients N, P and K in the soil.

[0041] (2) The method provided by the present invention can continuously reveal the migration, adsorption, fixation and transformation processes of phenanthrene on the surface of composite materials, soil particles, pore water and microbial communities through multi-time point, multi-scale and multi-parameter coupled analysis.

[0042] (3) The dynamic characterization system proposed by the method provided by the present invention can not only evaluate the removal effect of composite materials on phenanthrene, but also identify the degree of interface stabilization and long-term re-release risk, providing a quantitative basis for material screening and engineering applications. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a technical roadmap of the present invention; Figure 3This is a schematic diagram illustrating the changes in phenanthrene content and the evolution of key interface parameters at different time points in an embodiment of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] like Figures 1-3 As shown, this invention provides a method for the preparation and dynamic characterization of phenanthrene-based biochar-based removal from soil, which includes the following processes: Biomass raw materials are pretreated by washing, drying and crushing, and then subjected to oxygen-limited pyrolysis to obtain basic biochar. Biochar-based composite materials are obtained by introducing active metal components, mineral components and / or organic functional components through composite modification. The resulting composite material was added to contaminated soil in the Philippines to construct a multi-media interaction system; Perform timing sampling according to the set time nodes; The samples were analyzed for phenanthrene content, pore structure, functional groups, micro-region morphology and elemental distribution, wettability, and microbial behavior. Combined with kinetic model fitting, the micro-interface behavior and dynamic evolution of the composite material in removing phenanthrene from the soil were systematically characterized.

[0046] Appendix Figure 3 The technical route shown also indicates that this invention not only focuses on the phenanthrene removal results at the remediation endpoint, but also focuses on the changes in phenanthrene content and the evolution of key interface parameters at different time points. Through multi-timescale data acquisition and model fitting, the differences in the role of composite materials in the early, middle and late stages of remediation are identified, thereby revealing the changing patterns of adsorption, diffusion, fixation, synergistic degradation and re-release risks.

[0047] Biochar materials are obtained from biomass such as crop straw, manure, and municipal waste through oxygen-limited high-temperature pyrolysis. Wheat straw is washed, air-dried, and crushed, then treated in a carbonization furnace at 300 ℃ for 3 h with oxygen limitation. After cooling to room temperature, the carbonized material is removed and labeled BC. Nano-hydroxyapatite (HAP) can be successfully obtained from sources such as mineral rocks, plants, animal bones (fish bones, chicken bones), and biological products (eggshells, mussels). Due to its good ion exchange and adsorption capacity, it has good prospects for the treatment of air, water, and soil pollution. It is also a special type of biomaterial due to its good biocompatibility, biodegradability, and bioactivity. It is also a sustainable, safe, and clean method for pollutant removal and a valuable resource recycling pathway.

[0048] The material resulting from the composite of biochar (BC) and hydroxyapatite (HAP) in this application is referred to as BC-HAP (BH series and NBH series), and the specific composite process of this material is as follows: A certain mass of hydroxyapatite was weighed into a three-necked flask, a certain amount of deionized water was added and stirred for half an hour, the temperature was raised to 85 ℃, biochar was added and stirring was continued for 24 h, then the mixture was filtered, and finally the solid product obtained by filtration was placed in a vacuum drying oven and dried at 65 ℃.

[0049] Different composite ratios of biochar (BC) and hydroxyapatite (HAP) were used to prepare BC-HAP composite biochar-based materials. The BH series of HAP and BC composite materials were named BH1, BH2, BH3, and BH4, respectively. The NBH series of HAP and NaOH-BC composite materials were named NBH1, NBH2, NBH3, and NBH4, respectively.

[0050] Example 1 Preparation and dynamic characterization of iron-manganese composite oxide-supported biochar-based composite materials; Corn stalks were selected as the biomass raw material. They were first thoroughly washed with deionized water to remove surface mud and soluble impurities, then dried at 80℃ to constant weight, pulverized, and passed through a 100-mesh sieve. The treated raw material was placed in an oxygen-limited pyrolysis furnace and heated to 500℃ at a rate of 10℃ / min under nitrogen protection, held at this temperature for 2 hours, and then cooled to obtain basic biochar. This process corresponds to the flow chart in the attached diagram: "Biomass raw material (washing, drying, pulverizing) — oxygen-limited pyrolysis — obtaining basic biochar".

[0051] Iron and manganese salt solutions were prepared separately, mixed at a predetermined molar ratio, and added to the base biochar. The mixture was stirred and impregnated at 25°C for 12 h. Subsequently, the pH of the solution was adjusted to 9–10, allowing the iron-manganese composite oxide to deposit in situ on the biochar surface. After filtration, washing, and drying, a second heat treatment was performed at 300°C for 1 h to obtain the iron-manganese composite oxide-supported biochar-based composite material. This modification method is one of the specific implementation forms of the "composite modification (impregnation / co-precipitation / hydrothermal / ball milling / in-situ loading, introducing active metal components, mineral components, and organic functional components)" shown in the attached figure.

[0052] Topsoil from farmland, dried and sieved through a 100-mesh sieve, was collected. Phenylacetium was dissolved in acetone and sprayed evenly onto the soil to achieve an initial phenylacetium concentration of 100 mg / kg. After the organic solvent evaporated, the soil was aged at 25°C in the dark for 7 days to obtain phenylacet-contaminated soil. The prepared composite material was added to the phenylacet-contaminated soil at 3% of its mass, and the soil moisture content was adjusted to 60% of its maximum water holding capacity. The soil was then incubated at 25°C for 28 days to construct a multi-media interaction system of composite material, soil, pore water, and microorganisms. The dosage, initial pollutant concentration, and incubation period all fall within the range of the technical route shown in the attached figure.

[0053] Soil, pore water, material surface, and microbial samples were collected at 0, 1, 3, 7, 14, and 28 days. These sampling time points are consistent with the time point design in the attached figures, reflecting the dynamic differences in the initial rapid response phase, the intermediate interface regulation phase, and the later stabilization phase of remediation.

[0054] The total phenanthrene content in the soil and the extractable phenanthrene content in the pore water were determined using gas chromatography-mass spectrometry (GC-MS). Surface area analysis and pore size distribution analysis were used to analyze pore structure changes. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to analyze the changes in the chemical states of oxygen-containing functional groups and iron and manganese elements on the surface. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to observe the adhesion of soil particles and element migration characteristics on the material surface. Contact angle was used to determine the surface wettability of the material. Laser confocal microscopy was used to observe the formation process of microbial biofilms on the material surface. The above analytical items correspond to the phenanthrene content analysis, pore structure analysis, functional group analysis, micro-area morphology and elemental distribution analysis, wettability analysis, and microbial behavior analysis shown in the attached figures.

[0055] The obtained data were fitted with a pseudo-second-order kinetic model and an intraparticle diffusion model, and a comprehensive judgment was made by combining the changes in phenanthrene content and the evolution of key interface parameters at different time points.

[0056] The results showed that in the early stage of cultivation, phenanthrene mainly underwent rapid migration and surface adsorption from soil pore water to the material surface, manifested as a rapid decrease in total and extractable phenanthrene, significant changes in contact angle, and rapid occupation of surface active sites. In the middle and late stages of cultivation, the main manifestations were intrapore diffusion, site rearrangement, and enhanced microbial synergy, with more obvious biofilm attachment and element migration characteristics on the material surface. By day 14, the interface stabilization index had significantly increased, and the risk of re-release remained at a low level at day 28, indicating that iron-manganese composite oxide-supported biochar could not only achieve rapid initial fixation of phenanthrene but also maintain high interfacial stability in the later stages. This result is consistent with the dynamic characterization approach of "changes in phenanthrene content and evolution of key interfacial parameters at different time points" in Appendix 3.

[0057] Example 2 Preparation and dynamic characterization of bentonite / biochar composite materials; Rice husks were selected as raw material, washed, dried, and then subjected to oxygen-limited pyrolysis at 450℃ for 2 h to obtain rice husk biochar. The rice husk biochar was mixed with bentonite at a mass ratio of 4:1 and ball-milled for 4 h to obtain a bentonite / biochar composite material. This preparation process represents another representative implementation of the "biomass raw material pretreatment—oxygen-limited pyrolysis—composite modification" technical route shown in the attached figure. In this process, bentonite is introduced as a mineral component, and ball milling is used as a composite modification method to improve the material's surface roughness, interlayer structural coupling, and pore-filling and adsorption stabilization capacity for phenanthrene.

[0058] Contaminated soil from a coking site, dried and sieved through a 100-mesh sieve, was collected. Phenanthrene was dissolved in acetone and sprayed evenly onto the soil to achieve an initial concentration of 80 mg / kg. After the organic solvent evaporated, the soil was aged at 25°C in the dark for 7 days to obtain phenanthrene-contaminated soil. The resulting composite material was added to the contaminated soil at 5% of the soil mass and cultured at 30°C with a soil moisture content of 55% of maximum water holding capacity for 28 days.

[0059] Samples were taken at 0, 3, 7, 14, 21, and 28 days. The phenanthrene content was determined by high-performance liquid chromatography (HPLC), Raman spectroscopy was used to characterize changes in the material's aromatic structure, atomic force microscopy was used to characterize interfacial roughness, and phospholipid fatty acid analysis and dehydrogenase activity assays were used to analyze changes in microbial activity. Based on the technical route shown in Figure 3, this embodiment can be understood as a dynamic tracking process centered around "phenanthrene content—material structure—interfacial roughness—microbial behavior."

[0060] The results showed that in the early stages of cultivation, the composite material primarily reduced the bioavailability of phenanthrene through hydrophobic partitioning and pore filling, manifested as a rapid decrease in phenanthrene content and improved pore structure accessibility. In the middle and later stages of cultivation, the composite material promoted the synergistic degradation of phenanthrene by in-situ microorganisms by improving the soil microenvironment and material surface adhesion conditions, manifested as enhanced microbial activity, changes in material interface roughness, and aromatic structure response. Therefore, the mechanism of action of the bentonite / biochar composite material exhibits a clear phased pattern: in the early stages, physical adsorption and pore filling control are dominant, while in the later stages, synergistic microbial action and interface stabilization are dominant. This phased characteristic also aligns with the... Figure 1 and 3 The technical concept is "initial rapid action - mid-to-late stage dynamic evolution - collaborative determination of key parameters".

[0061] Example 3 Preparation of magnetic calcium-based mineral / biochar composites and dynamic characterization of their re-release risk Wood chips were selected as raw material and subjected to limited oxygen pyrolysis at 550℃ for 2 h to obtain basic biochar. Fe3O4 magnetic components and calcium-based minerals were co-loaded onto the surface of the biochar using an impregnation-calcination method to obtain a magnetic calcium-based mineral / biochar composite material. This material possesses the capabilities of magnetic separation, mineral immobilization, and interface regulation, and is a specific embodiment of the composite modification involving the introduction of active metal and mineral components shown in the attached figure.

[0062] Air-dried farmland soil that had passed through a 100-mesh sieve was collected. Phenylacetium was dissolved in acetone and sprayed evenly onto the soil to achieve an initial phenylacetium concentration of 120 mg / kg. After the organic solvent evaporated, the soil was aged at 25°C in the dark for 7 days to obtain phenylacet-contaminated soil. The resulting composite material was added to the phenylacet-contaminated soil at 2% of the soil mass and cultured at 25°C and a soil moisture content of 60% of maximum water holding capacity for 28 days. An alternating aerobic / intermittent flooding environment was set up to simulate soil disturbance.

[0063] Sampling was conducted at 0, 1, 7, 14, 21, and 28 days to determine the total phenanthrene, extractable phenanthrene, and phenanthrene content in the adsorbed phase of the material. A partial least squares regression model was established using X-ray photoelectron spectroscopy, contact angle, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and high-throughput sequencing data. Although this embodiment additionally employed a partial least squares regression model, its underlying data sources remain consistent with the dynamic characterization framework presented in the attached figures. Specifically, it comprehensively identifies interfacial failure and re-release risks through phenanthrene content analysis, functional group / elemental state analysis, wettability analysis, micro-region morphology and elemental distribution analysis, and microbial behavior analysis.

[0064] The results show that under environmental disturbance conditions, if the oxygen-containing functional groups on the material surface decrease, the contact angle increases, and the microbial abundance decreases, the risk factor of re-release will increase. The dynamic characterization method of the present invention can identify the potential failure risk caused by the passivation and weakening of the material surface and the fixation ability at an earlier stage.

[0065] Further combine with the appendix Figure 3 The proposed approach, which explores "changes in phenanthrene content and evolution of key interfacial parameters at different time points," demonstrates that the risk of re-release does not manifest only at the endpoint but rather exhibits predictable characteristics in the mid-to-late stages through changes in several interfacial parameters. This suggests that the method described in this invention, compared to simple endpoint determination, is more suitable for assessing the long-term stabilization capability of materials under perturbed conditions.

[0066] Example 4 Comparison of long-term restoration effects under different restoration materials and quality gradients In addition, nine 10.0 g samples of contaminated soil containing the organic pollutant phenanthrene were accurately weighed into 100 ml stoppered plastic centrifuge tubes. Remediation materials BC, NaOH-BC, BH2, and NBH3 were added respectively. Two mass gradients were set up, with 5% and 10% of the remediation materials added, and the remaining sample served as a control group. The effect of different remediation times on the remediation effect was observed, with time gradients of 3 days, 7 days, 14 days, 21 days, 42 days, and 84 days, and data were recorded. This embodiment extends the later observation time to 42 days and 84 days based on the standard time nodes shown in the attached figure to enhance the tracking of long-term remediation effects and later stabilization behavior. Although 42 days and 84 days are not among the core time nodes listed in the attached figure, they are consistent with the concept of "follow-up dynamic evolution tracking" illustrated in the figure.

[0067] The specific surface area was determined using the Bruauer-Emmett-Teller (BET) technique, and the microporous specific surface area was calculated using the t-plot method. The specific surface areas of BH2 and NBH3 were 31.31 and 34.21 m² / g, respectively, which were nearly 6 and 7 times larger than those of BC. This is mainly because hydroxyapatite was loaded on the surface or within the pores of the biochar, playing a compensatory role. (See attached...) Figure 3 The pore structure analysis revealed that increased pore structure helps improve the material's contact opportunities with phenanthrene, the number of diffusion channels, and the accessibility of adsorption sites.

[0068] When the biochar application rate was 10%, the increases in soil nutrients N, P, and K were most significant, increasing by 1.9, 0.5, and 11.4 times, respectively. The total removal rates reached their maximum when the application rate of biochar and modified biochar was 1.0 g and the removal time was 84 days, at 6.96% and 29.95%, respectively. This indicates that the amount of material applied, pore structure characteristics, and the introduction of mineral functional components all affect the soil physicochemical environment and microbial niche, thus significantly influencing the long-term removal and stabilization of phenanthrene. Combining this with the microbial behavior analysis, pore structure analysis, and kinetic fitting framework shown in the attached figures further explains the sources of differences in remediation effects among different materials.

[0069] It should be noted that the materials BC, NaOH-BC, BH2, and NBH3 in this embodiment can serve as control groups for materials with different modification paths and functional characteristics, illustrating the influence of material pore structure, surface functional groups, and mineral loading methods on the repair behavior. Although this embodiment mainly demonstrates long-term repair effects, according to the technical solution of this invention, pore water, material surface, and microbial samples can also be collected simultaneously at 3d, 7d, 14d, 21d, 42d, and 84d, and phenanthrene content analysis, functional group analysis, micro-area morphology and elemental distribution analysis, wettability analysis, and microbial behavior analysis can be carried out to construct a more complete long-term dynamic characterization data chain.

[0070] Comparison of proportions If only the residual amount of phenanthrene in the soil is measured at the end of the cultivation period, without standardized control of the composite material preparation process, and without time-series sampling and synergistic characterization of pore water, interface morphology, surface functional groups, wettability, and microbial behavior, then only the removal results of the material at a single time point can be obtained. It is difficult to distinguish the relative contributions of stages such as rapid surface adsorption, slow diffusion in pores, interface stabilization, and synergistic degradation by microorganisms, and it is also impossible to effectively determine the long-term stabilization degree and re-release trend of phenanthrene during the remediation process.

[0071] Furthermore, without the technical support shown in the attached figure, i.e., without conducting phenanthrene content analysis, pore structure analysis, functional group analysis, micro-area morphology and elemental distribution analysis, wettability analysis, and microbial behavior analysis at different time points, and without combining pseudo-first-order / pseudo-second-order kinetic models, Elovich models, intraparticle diffusion models, and Fick diffusion models for multidimensional fitting, it is impossible to reveal the intrinsic relationship between changes in phenanthrene content and the evolution of key interface parameters at different time points, and it is also impossible to accurately determine whether the material has undergone surface passivation, pore blockage, active site attenuation, or a decrease in microbial synergistic ability.

[0072] Therefore, compared with conventional remediation evaluation methods that only compare endpoint concentrations, this invention introduces a complete process of material preparation, soil interaction, time-series sampling, multidimensional characterization, and kinetic determination. This not only evaluates the immediate removal effect of materials but also identifies the dominant mechanisms of materials in different remediation stages, thereby enabling more reliable predictions of long-term stabilization capacity and potential re-release risks.

[0073] Concluding remarks The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Equivalent substitutions, parameter adjustments, or process optimizations made by those skilled in the art regarding raw material types, composite components, preparation conditions, characterization methods, data processing models, and their combinations without departing from the spirit and substance of the present invention should all fall within the scope of protection of the present invention.

[0074] Appendix Figure 1-3 The process, technical route, and dynamic evolution diagram shown can all serve as useful supplements and explanatory basis for the embodiments of the present invention, and are used to illustrate how the present invention achieves dynamic analysis of the remediation process of Fiber-contaminated soil from material preparation, system construction, time-series sampling, multi-source characterization to kinetic fitting. However, they should not be construed as additional limitations on the scope of protection of the present invention.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the preparation and dynamic characterization of a biochar-based removal of phenanthrene in soil, characterized by, The method includes the following steps: 1) Select biomass raw materials, and obtain basic biochar through drying, pulverizing and oxygen-limited pyrolysis treatment; 2) The basic biochar is combined with one or more of the following components: active metal components, mineral components, and organic functional components to obtain a biochar-based composite material; 3) The biochar-based composite material was added to phenanthrene-contaminated soil to construct a multi-media system for removing phenanthrene from the soil using the composite material; 4) Under preset incubation conditions, soil samples, pore water samples, material interface samples, and microbial samples were collected sequentially in the multi-media interaction system according to the time gradient; 5) By measuring the pollutant concentration, characterizing the interface physicochemical properties, and analyzing the micro-region structure of the samples obtained in step 4), and combining the analysis results with the kinetic model fitting, the migration, adsorption, fixation, transformation and re-release processes of phenanthrene in the micro-interface between biochar-based composite materials and soil multi-media were dynamically characterized.

2. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, In step 1), the biomass raw material is one or more of straw, sawdust, rice husk, fruit shell, sludge, and livestock and poultry manure; the temperature of the oxygen-limited pyrolysis is 400-700℃, and the pyrolysis time is 1-4 h.

3. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, In step 2), the active metal component is one or more of the oxides, hydroxides or salts of iron, manganese, calcium and magnesium; the mineral component is one or more of bentonite, kaolin, zeolite, hydroxyapatite, attapulgite and montmorillonite; and the organic functional component is one or more of humic acid, humate or oxygen- or nitrogen-containing organic modifiers.

4. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1 or 3, characterized in that, In step 2), the composite modification method is one or more of the following: impregnation method, co-precipitation method, hydrothermal method, ball milling method, in-situ loading method, and ultrasonic-assisted method.

5. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, In step 3), the initial concentration of phenanthrene in the phenanthrene-contaminated soil is 50–500 mg / kg; the dosage of the biochar-based composite material is 1%–5% of the soil mass; the culture temperature of the multi-media system is 25–30℃; the soil moisture content is 50%–70% of the maximum water holding capacity; and the culture time is 7–84 days.

6. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, In step 4), the time gradient includes at least four time points selected from 0 d, 1 d, 3 d, 7 d, 14 d, 21 d and 28 d.

7. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, In step 5), the pollutant concentration is determined using high-performance liquid chromatography, gas chromatography, or gas chromatography-mass spectrometry; the interface physicochemical characterization includes one or more of functional group analysis, wettability analysis, and pore structure analysis, wherein the functional group analysis uses one or more of Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy; the wettability analysis uses contact angle measurement; the pore structure analysis uses one or more of specific surface area analysis and pore size distribution analysis; the micro-area structure characterization includes one or more of scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, and laser confocal microscopy to analyze micro-area morphology and elemental distribution.

8. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, Step 5) also includes microbial behavior characterization, which employs one or more of the following: high-throughput sequencing, phospholipid fatty acid analysis, dehydrogenase activity assay, catalase activity assay, fluorescence staining, or extracellular polymer characterization.

9. The method for preparing and dynamically characterizing biochar-based phenanthrene removal from soil according to claim 1, characterized in that, In step 5), the kinetic model fitting includes one or more of the following: pseudo-first-order kinetic model, pseudo-second-order kinetic model, Elovich model, intraparticle diffusion model, and Fick diffusion model. Based on the fitting results, one or more of the following are calculated: interfacial adsorption rate constant, apparent desorption coefficient, interfacial diffusion coefficient, interfacial stabilization index, and re-release risk factor.

10. An application of the preparation and dynamic characterization method for removing phenanthrene from soil according to any one of claims 1-9, wherein the method is applied to the screening of biochar-based composite materials, the optimization of phenanthrene-contaminated soil remediation processes, and the risk assessment of polycyclic aromatic hydrocarbon-contaminated soil.

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