Environment-friendly additive for soil pollution remediation and application method thereof

Abstract

The invention relates to the technical field of environment-friendly additives, and discloses an environment-friendly additive for soil pollution remediation and an application method thereof.The environment-friendly additive is prepared from 5-20 parts of nano zero-valent iron, 2-15 parts of a nano carbon material and 3-18 parts of a nano mineral composite material; 5-25 parts of biochar, 2-10 parts of microbial flora and 1-10 parts of a plant source extract; 1-8 parts of a pH responsive material; 2-10 parts of a microcapsule material; the particle size range of the nanoscale zero-valent iron is 10-100 nm, and SiO2 or C is coated on the surface of the nanoscale zero-valent iron; the nano carbon material is selected from activated carbon nanoparticles, graphene and carbon nanotubes. The carbon-coated nano zero-valent iron is adopted, so that the technical effects of improving the oxidation resistance of the material and prolonging the active life are achieved. Compared with a traditional technical scheme without coating nZVI, the problems that the composite material is prone to oxidation inactivation and insufficient in long-term repair capacity are solved, and the composite material has more stable heavy metal removal performance in a complex environment.

Description

Technical Field

[0001] The present invention relates to the technical field of environment-friendly additives, specifically to an environment-friendly additive for soil pollution remediation and its application method. Background Art

[0002] The problem of environmental pollution is becoming increasingly prominent. Especially heavy metal pollution in soil and groundwater poses a serious threat to the ecosystem and human health. Due to the persistence and non-degradability of heavy metals, traditional physical remediation (such as soil replacement), chemical remediation (such as precipitation, complexation) and bioremediation methods often have problems such as high cost, low efficiency and limited scope of application. Therefore, developing efficient and sustainable heavy metal pollution remediation technologies has become the current research focus.

[0003] In the prior art, nano zero-valent iron (nZVI) has been widely used in the field of pollution remediation due to its high reactivity and good electron donor properties. Research shows that nZVI can effectively remove heavy metals in water and soil through mechanisms such as reduction precipitation and complexation adsorption. However, traditional nZVI has the defects of easy oxidation inactivation and short action time, which affect its long-term remediation ability. To improve the stability of nZVI, some studies have adopted methods such as carbon coating and alloy doping, combined with pH regulation and slow-release systems to optimize the remediation effect.

[0004] However, the prior art still has limitations in the stable release of remediation agents. Most remediation materials have too fast a release rate in a short time after being put in, resulting in a significant initial remediation effect, but a decline in the long-term removal ability, ultimately affecting the sustainability of pollution treatment. Therefore, how to improve the slow-release performance of remediation agents to achieve long-term and effective removal of pollutants is still a technical problem to be solved urgently. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides an environment-friendly additive for soil pollution remediation and its application method, solving the problem that the release rate of the remediation agent is uncontrollable, the initial release is too fast, the later effect decays, resulting in insufficient long-term heavy metal removal ability.

[0006] To achieve the above purposes, the present invention is realized through the following technical solutions: An environment-friendly additive for soil pollution remediation, including the following mass components: 5-20 parts of nano zero-valent iron, 2-15 parts of nano carbon material, 3-18 parts of nano mineral composite material; 5-25 parts of biochar, 2-10 parts of microbial flora, 1-10 parts of plant-derived extract; 1-8 parts of pH-responsive material; 2-10 parts of microcapsule material.

[0007] Preferably, the particle size range of the nano zero-valent iron is 10-100nm, and it is surface-coated with SiO 2or C; The nano-carbon material is selected from activated carbon nanoparticles, graphene, and carbon nanotubes; The nano-mineral composite material is prepared by compound modification of montmorillonite, attapulgite, zeolite, and iron oxide, and is activated at a high temperature of 300-600 °C.

[0008] Preferably, the microbial flora includes: Heavy metal degrading bacteria: Bacillus subtilis, Pseudomonas, Actinomycetes; Petroleum hydrocarbon degrading bacteria: Pseudomonas petroleum, Aspergillus oryzae; Pollution-resistant Actinomycetes: Streptomyces; The microbial flora is cultured by liquid fermentation and can be combined with a biochar carrier.

[0009] Preferably, the pH-responsive material includes: Polymers: poly(lactic-co-glycolic acid), sodium polyacrylate; Inorganic materials: calcium carbonate, magnesium carbonate; Its pH response regulation range is 5-8. Under low pH conditions, pH ≤ 5.5, dissolution is accelerated, and under high pH conditions, pH ≥ 7.5, release is delayed.

[0010] Preferably, the microcapsule material is selected from sodium alginate microcapsules, chitosan microcapsules, and starch-based microcapsules, and is used to control the release rate of the core material for pollutant removal and the microbial flora, and the release time can reach 30-120 days.

[0011] The application method of the environment-friendly additive for soil pollution remediation includes the following steps: Pollutant detection: Atomic absorption spectrometry is used to detect heavy metal ions, with a detection limit of 0.01 mg / L; Gas chromatography-mass spectrometry is used to detect organic pollutants, with a detection limit of 0.001 mg / L; Dosage calculation and preparation: According to the detection results, calculate the dosage of the additive required and mix it with an appropriate amount of water or carrier to prepare a suspension or powder; Heavy metal pollution remediation: The additive is evenly sprayed or mixed into the contaminated soil, and the applicable pH range is 6.0-8.0; Petroleum hydrocarbon pollution remediation: The high-pressure injection or tillage mixing method is adopted, and the applicable soil humidity is 30-50%; Pesticide residue pollution remediation: The surface spreading combined with irrigation infiltration method is adopted, and the applicable pH range is 5.5-7.5; Remediation monitoring: Samples are taken every 15-30 days to analyze the degradation of pollutants, and the dosage of the additive is adjusted Preferably, it is applicable to acidic soils with a pH of 4.5 - 6.5, neutral soils with a pH of 6.5 - 7.5, and alkaline soils with a pH of 7.5 - 8.5; The remediation periods for different pollutants are as follows: heavy metal pollution: 60 - 180 days; petroleum hydrocarbon pollution: 30 - 90 days; pesticide pollution: 20 - 60 days.

[0012] Preferably, after application, the degradation of pollutants is regularly detected every 15 - 30 days; If the pollutant removal rate is lower than 50%, adjust the additive formula, including: Increase the dosage of 10 - 30% nano zero - valent iron or nano - mineral composite materials; Adjust the proportion of pH - responsive materials; Re - inoculate the microbial flora.

[0013] Preferably, the application equipment includes spraying equipment, tillage mixing equipment, and high - pressure injection equipment; The suitable temperature range for application is 10 - 35°C, and the suitable soil humidity range is 30 - 50%.

[0014] The present invention provides an environment - friendly additive for soil pollution remediation and its application method. It has the following beneficial effects: 1. The present invention uses carbon - coated nano zero - valent iron, achieving the technical effect of improving the antioxidant property of the material and extending the active life. Compared with the traditional technical solution without coated nZVI, it solves the problems of easy oxidation and inactivation and insufficient long - term remediation ability, enabling it to have more stable heavy metal removal performance in complex environments.

[0015] 2. The present invention utilizes a pH - responsive regulation system, achieving the technical effect of optimizing the remediation environment and improving the heavy metal fixation efficiency. Compared with the technical solution that simply relies on chemical pH adjustment, it solves the problems of drastic pH fluctuations and damaged microbial environments, thus realizing a more gentle and sustainable soil remediation.

[0016] 3. The present invention adopts a slow - release remediation agent encapsulation technology, achieving the technical effect of extending the release period of the remediation agent and improving the stability of heavy metal removal. Compared with the traditional technical solution of instant - release remediation agents, it solves the problems of too fast initial release and attenuation of later effects, making the remediation process more balanced and efficient, and avoiding resource waste.

[0017] 4. The present invention combines the synergistic effects of multifunctional materials, achieving the technical effect of enhancing the pollutant fixation ability and improving the long - term adaptability of the remediation system. Compared with the technical solution of single - component remediation agents, it solves the problems of poor targeting and insufficient environmental adaptability, enabling the remediation system to maintain excellent treatment capabilities under different pollution conditions. Description of the Drawings

[0018] Figure 1 Schematic diagram of the method flow of the present invention. Specific implementation mode

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] Please refer to the attached Figure 1 , the embodiments of the present invention provide an environment-friendly additive for soil pollution remediation and its application method, including: The additive is composed of nano zero-valent iron, nano carbon material, nano mineral composite material, biochar, microbial flora, plant-derived extract, pH-responsive material, slow-release material, etc.

[0021] In order to ensure the remediation efficiency, the proportion of each component has been repeatedly optimized to ensure the removal rate of pollutants and the material stability. The preparation steps are as follows: (1) Preparation of nano zero-valent iron (nZVI) Using the liquid-phase reduction method, with FeCl 3 •6H 2 O as the iron source and NaBH 4 as the reducing agent, nano zero-valent iron is prepared under N 2 protection.

[0022] After the reaction is completed, wash it 3 times with deionized water, then dehydrate it with ethanol, and finally dry it in a vacuum environment to obtain nZVI with a particle size of 30-50 nm.

[0023] Surface coating: Disperse nZVI in an ethanol solution, add SiO 2 sol or glucose solution, and form a protective layer through hydrolysis-polymerization reaction. This can prevent nZVI from being rapidly oxidized in the air and improve the stability.

[0024] nZVI reduces and precipitates heavy metals (such as Cr 0 →Fe 2+ →Fe 3+ ) through the oxidation process of Fe 6+ , Pb 2+ ), and at the same time can catalyze the Fenton reaction to degrade organic pollutants. SiO 2 or carbon coating can improve the dispersibility and persistence of the material in the soil and prevent agglomeration.

[0025] (2) Preparation of nano carbon material Activated carbon nanoparticles, graphene, and carbon nanotubes are selected as raw materials.

[0026] Activated carbon nanoparticles: The carbonization-activation method is used. Using fruit shells or bamboo charcoal as raw materials, carbonize at 800 °C in a nitrogen atmosphere for 2 h, and then activate at 850 °C in a CO 2 atmosphere for 1 h to obtain activated carbon nanoparticles with a high specific surface area.

[0027] Graphene: Graphene oxide (GO) is prepared by oxidizing graphite using the Hummers method, and then reduced to reduced graphene oxide (rGO).

[0028] Carbon nanotubes: Prepared by chemical vapor deposition (CVD) method, using methane as the carbon source and nickel as the catalyst, reacting at 700 - 900 °C for 3 h.

[0029] Activated carbon nanoparticles can adsorb organic pollutants such as polycyclic aromatic hydrocarbons and petroleum hydrocarbons relying on their porous structure and π-π interactions.

[0030] The ultra-high specific surface area and hydrophobicity of graphene can enhance the adsorption of organic pollutants.

[0031] Carbon nanotubes can serve as an electron transport medium to promote the oxidation degradation reaction.

[0032] (3) Preparation of nano-mineral composites Montmorillonite, attapulgite, zeolite, and iron oxide are used as basic materials.

[0033] Modification treatment: Montmorillonite is exchanged in 3 mol / L NaCl solution for 24 h, and then washed with deionized water until the Cl - content is less than 10 ppm, and finally activated at 400 °C for 2 h to improve the adsorption capacity.

[0034] Zeolite is acid-modified + thermally activated (soaked in 1 M HCl for 12 h, followed by calcination at 500 °C) to enhance the adsorption capacity for heavy metal ions.

[0035] Iron oxide (Fe 3 O 4 ) nanoparticles are prepared by the co-precipitation method, that is, Fe 2+ / Fe 3+ are mixed in a molar ratio of 1:2, and the pH is adjusted to 10 in NH 4 OH solution to generate Fe 3 O 4 nanoparticles.

[0036] The layered structure of mineral materials such as montmorillonite can immobilize heavy metals through ion exchange and complexation adsorption.

[0037] Iron oxide nanoparticles capture heavy metal ions through magnetic adsorption, improving the remediation efficiency.

[0038] 1.2 Preparation of auxiliary materials (4) Cultivation of microbial flora Select strains such as Bacillus subtilis, Pseudomonas, Actinomycetes, Pseudomonas oleovorans, and Aspergillus oryzae, and culture them in LB medium (for bacteria) and PDA medium (for fungi) respectively.

[0039] After culturing in a shaker at 37°C for 24 - 48 h, collect the bacterial liquid and prepare bacterial powder by freeze-drying method.

[0040] Immobilization of flora: Mix the bacterial liquid with biochar, let it stand and adsorb for 12 h, and then spray-dry to obtain immobilized microbial bacterial powder.

[0041] Microbial degradation: Utilize the metabolic enzyme system of microorganisms to convert pollutants into harmless substances. For example, Pseudomonas can produce siderophores to promote Fe 3+ reduction and improve the activity of nZVI.

[0042] Biochar immobilization: Improve the survival rate of microorganisms and extend the action time of the remediation agent.

[0043] (5) Preparation of pH-responsive materials Use materials such as PLGA, sodium polyacrylate, calcium carbonate, and magnesium carbonate, and mix them in a ratio of 1:1:1.

[0044] PLGA is prepared by emulsion polymerization to form nanoscale microspheres.

[0045] Calcium carbonate and magnesium carbonate are prepared by coprecipitation method, and the particle size is controlled at 200 - 500 nm.

[0046] In an acidic environment, the degradation rate of PLGA accelerates, and the release of pollutant remover accelerates.

[0047] Calcium carbonate and magnesium carbonate slowly release Ca 2+ / Mg 2+ to play a pH buffering role and prevent the soil from being too acidic and affecting the microbial activity.

[0048] (6) Preparation of slow-release materials Use sodium alginate, chitosan, and starch to prepare microcapsules to encapsulate the core material.

[0049] Ultrasonically disperse the core material for pollutant removal in the chitosan solution, and drop it into the CaCl 2 solution to form microcapsules.

[0050] Microcapsules can control the release rate of the remediation agent, prevent the microbial flora from dying too quickly, and ensure long-term remediation ability.

[0051] Application method: Spraying method: Suitable for surface pollution, with a dosage of 3 - 5 kg per mu. After being formulated into a suspension, it is sprayed.

[0052] Tillage mixing method: Suitable for deep - layer pollution. Through soil - turning machinery for mixing, ensure uniform distribution.

[0053] High - pressure injection method: Suitable for underground pollution. Using a high - pressure pump to inject the remediation agent into the polluted layer, with a penetration radius of up to 1 m.

[0054] Example 1: This example provides an environment - friendly additive for soil pollution remediation and its application method, specifically including the following steps: Raw material ratio (mass percentage): 25% nano - zero - valent iron (nZVI), 20% activated carbon nanoparticles, 15% montmorillonite - modified powder, 10% Pseudomonas bacteria; 10% pH - responsive material (PLGA + calcium carbonate); 10% slow - release material (sodium alginate + chitosan); the remaining part: deionized water Preparation of nano - zero - valent iron: Using FeCl 3 •6H 2 O as the iron source and NaBH 4 as the reducing agent, reacting for 30 min under N 2 atmosphere, controlling the temperature at 20°C and the stirring speed at 500 rpm.

[0055] The product is washed three times with deionized water, dehydrated with ethanol, and vacuum - dried. Finally, nZVI powder with a particle size of about 40 nm is obtained.

[0056] Preparation of activated carbon nanoparticles: Selecting coconut shell carbonized at 800°C for 2 h and activated at 850°C for 1 h under CO 2 atmosphere, and grinding to a particle size less than 100 nm.

[0057] Enhance the adsorption of petroleum hydrocarbons through π - π interaction and pore adsorption capacity.

[0058] Montmorillonite modification: Exchange montmorillonite in 1M NaCl solution for 12 h to improve the ion - exchange capacity.

[0059] Calcinate at 400°C for 2 h to promote lattice rearrangement and improve the heavy - metal adsorption performance.

[0060] Preparation of Pseudomonas bacteria powder: Cultivate at 37°C for 48 h, centrifuge to collect the bacterial liquid, and freeze - dry to obtain the bacterial powder.

[0061] Complex heavy metals through extracellular polymeric substances to improve the remediation effect.

[0062] pH-responsive materials and sustained-release systems: PLGA is prepared by emulsion polymerization with a particle size of 200 nm; calcium carbonate is prepared by coprecipitation with a particle size of 500 nm.

[0063] Mix sodium alginate and chitosan to form a stable microcapsule structure to encapsulate the remediation agent.

[0064] Application effect: Spray 3 kg / m 2 on the contaminated soil, and the removal rate of lead (Pb 2+ ) is increased to 85%.

[0065] The degradation rate of petroleum hydrocarbons reaches 90%, and the recovery rate of soil microbial diversity is 95%.

[0066] Example 2: This example provides an environment-friendly additive for soil pollution remediation and its application method, which specifically includes the following steps: Raw material ratio (mass percentage): nano zero-valent iron (carbon-coated): 30%, reduced graphene oxide (rGO): 15%, zeolite modified powder: 20%, Bacillus subtilis powder: 10%, pH-responsive material (PLGA + magnesium carbonate): 10%, sustained-release material (sodium alginate): 10%, the remaining part: deionized water; Carbon-coated nano zero-valent iron: Hydrothermal method is used, with glucose solution as the carbon source, reacting at 180 °C for 6 h to form a carbon layer coating nZVI and improve the antioxidant ability.

[0067] Preparation of reduced graphene oxide (rGO): Graphene oxide is synthesized by the Hummers method and then reduced with vitamin C to obtain rGO.

[0068] rGO can serve as an electron transport channel to promote the precipitation of heavy metal ions.

[0069] Zeolite modification: Modified with 1M HCl for 12 h and calcined at 500 °C to increase the specific surface area and adsorption capacity.

[0070] Bacillus subtilis powder: Complex heavy metals through extracellular polymeric substances to improve the removal ability of Cd²⁺ and Pb²⁺.

[0071] pH-responsive material and sustained-release system: Magnesium carbonate provides buffering capacity to prevent sudden changes in pH from affecting microbial activity.

[0072] Sodium alginate crosslinks to form gel microspheres to stably release the remediation agent.

[0073] Application effect: Inject into the underground contaminated layer under high pressure, with a dosage of 2 kg per square meter, and the removal rate of cadmium (Cd 2+ ) reaches 80%.

[0074] The degradation rate of organic pollutants is increased by 3 times, and the repair process can last for more than 90 days.

[0075] Example 3: This example provides an environment-friendly additive for soil pollution repair and its application method, which specifically includes the following steps: Raw material ratio (mass percentage): nano zero-valent iron + Fe 3 O 4 Composite material: 25%, carbon nanotubes: 20%, attapulgite modified powder: 15%, Pseudomonas aeruginosa powder: 10%, pH-responsive material (PLGA + calcium carbonate + magnesium carbonate): 10%, sustained-release material (sodium alginate + chitosan): 10%, the remaining part: deionized water Nano zero-valent iron-Fe 3 O 4 Composite material: Fe 2+ / Fe 3+ Co-precipitate in a ratio of 1:2 to form Fe 3 O 4 nano-particles in a pH 10 environment, combined with nZVI to improve the magnetic adsorption capacity.

[0076] Preparation of carbon nanotubes: Synthesized by CVD method at 800 °C to enhance electron transport ability and accelerate pollution degradation.

[0077] Modification of attapulgite: Exchange in 1M NaCl solution for 24 h to improve the interlayer cation exchange capacity and enhance the heavy metal fixation effect.

[0078] Pseudomonas aeruginosa powder: Cultured at 37 °C for 48 h, centrifuged to collect the bacterial liquid, and freeze-dried to enhance the petroleum hydrocarbon degradation ability.

[0079] pH-responsive material and sustained-release system: Calcium carbonate and magnesium carbonate provide buffering capacity, and PLGA microspheres ensure slow release of the repair agent.

[0080] Application effect: Using the tillage mixing method, apply 3.5 kg per mu, and the degradation rate of petroleum hydrocarbons reaches 95%.

[0081] The heavy metal removal rate is increased to 87%, and the repair effect is stable for more than 90 days.

[0082] Example 4: Due to the long-term storage of mine waste residues in a certain mining area tailings pond, the heavy metals (such as cadmium, lead, arsenic) in the soil exceed the standard, the pH value is lower than 4.5, the soil structure is loose, the microbial activity is low, and the ecological environment has seriously degraded. To treat this polluted area, the environmentally friendly soil remediation additive of the present invention is selected for the pollution remediation of the mine tailings pond.

[0083] 2. Pollutant Detection The atomic absorption spectrometry (AAS) was used to detect the heavy metal ion content in the tailings soil, and the results are as follows: Cadmium (Cd): 3.8 mg / kg (exceeding the standard limit value of 0.6 mg / kg); Lead (Pb): 120 mg / kg (exceeding the standard limit value of 80 mg / kg); Arsenic (As): 65 mg / kg (exceeding the standard limit value of 40 mg / kg).

[0084] A pH tester was used to measure the soil acidity and alkalinity, and pH = 4.3 (strongly acidic).

[0085] The soil microbial culture method was used to detect the soil microbial activity, and it was found that the number of microorganisms was extremely low.

[0086] 3. Additive Formula and Preparation Based on the pollutant detection results, an environmentally friendly soil remediation additive was formulated, and its mass components are as follows (calculated based on every 1000 kg of polluted soil): Nano zero-valent iron (nZVI): 15 kg (used for heavy metal reduction and precipitation); Nano mineral composite: 12 kg (a mixture of montmorillonite, attapulgite, and zeolite to enhance heavy metal adsorption capacity); Biochar: 20 kg (to adjust the soil structure and enhance the microbial attachment ability); pH-responsive material (calcium carbonate + poly(lactic-co-glycolic acid)): 5 kg (to increase the pH of the acidic tailings pond soil); Microbial flora: 6 kg (Bacillus subtilis, Pseudomonas, Streptomyces, etc.); Microcapsule material: 4 kg (to delay the release of active ingredients and continuously repair).

[0087] 4. Remediation Method Additive Application: The spraying method + deep plowing mixing method was used to evenly spread the additive on the surface of the polluted tailings soil and use a rotary tiller to plow to a depth of 30 cm; For areas with higher heavy metal concentrations, the high-pressure injection method was used to mix the remediation additive with water to form a suspension (mass ratio 1:5) and inject it deep into the soil layer through high-pressure spraying.

[0088] pH adjustment: After applying the pH-responsive material, the soil pH increased from 4.3 to 6.5 (monitoring data on the 10th day).

[0089] Heavy Metal Fixation: Nano-zero-valent iron undergoes a reduction-precipitation reaction with heavy metals, reducing their mobility; Nano-mineral composite materials + biochar further adsorb heavy metals and enhance the stabilization effect.

[0090] Microbial remediation: Apply heavy metal degrading bacteria (Bacillus subtilis, actinomycetes) to promote biodegradation of pollutants; Apply pollution-tolerant actinomycetes (Streptomyces) to restore soil microbial communities.

[0091] Vegetation recovery (after day 30): Choose pollution-tolerant plants ryegrass + ash tree for planting to absorb heavy metals in the soil and improve soil structure.

[0092] 5. Repair monitoring Day 15: Soil pH rises to 6.5, heavy metal mobility decreases, and microbial activity increases; Day 30: Soil Cd concentration decreased to 1.2 mg / kg, Pb decreased to 85 mg / kg, and As decreased to 42 mg / kg; Day 90: The heavy metal content in the soil meets the standard, the vegetation survival rate is 85%, and the soil microbial community has recovered well; Day 180: The soil in the tailings pond has restored its ecological functions, heavy metal residues have been reduced by more than 80%, and the vegetation coverage rate in the polluted area is >75%.

[0093] Comparative Example 1: Differences: Uncoated nano zero-valent iron is easily oxidized and becomes ineffective.

[0094] Without the addition of pH-responsive materials, the soil environment fluctuated greatly.

[0095] Without using a sustained-release system, the repair material is released too quickly, which is effective in the short term but ineffective later.

[0096] Preparation process: Preparation of nano zero-valent iron (nZVI): FeCl 3 •6H 2 O and NaBH 4 Reaction, N 2 The mixture was stirred at 500 rpm for 30 min under protection to generate nZVI.

[0097] No SiO2 Or carbon coating, followed by direct washing and drying.

[0098] Activated carbon nanoparticles: Carbonized at 800 °C for 2 h, activated at 850 °C for 1 h under a CO 2 atmosphere, with a particle size < 100 nm.

[0099] Montmorillonite modification: Exchanged with 1 M NaCl for 12 h, calcined at 400 °C for 2 h to improve the adsorption capacity.

[0100] Pseudomonas powder: Cultured at 37 °C for 48 h, the cells were collected by centrifugation and freeze-dried.

[0101] Mixing and application: Directly mix each component, without using a slow-release system, sprayed at 3 kg / m 2 .

[0102] Comparative example two: Differences: Carbon-coated nano zero-valent iron was not used, the oxidation rate increased, and the activity of the repair agent decreased.

[0103] pH-responsive material was not added, and the pH fluctuated violently during the repair process, affecting the microbial activity.

[0104] Unmodified zeolite has a lower ion exchange capacity, weakening the ability to remove heavy metals.

[0105] Preparation process: Nano zero-valent iron: FeCl 3 •6H 2 O and NaBH 4 reacted, reduced under a N 2 atmosphere for 30 min, 500 rpm, without carbon coating.

[0106] Reduced graphene oxide (rGO): Graphite was oxidized by the Hummers method and then reduced with vitamin C to obtain rGO.

[0107] Zeolite modification: Without acid modification and calcination, directly crushed to 100 nm.

[0108] Bacillus subtilis powder: Cultured at 37 °C for 48 h, the cells were collected by centrifugation and freeze-dried.

[0109] Mixing and application: Directly mix each component, without using a pH adjustment system, injected under high pressure at 2 kg / m 2 .

[0110] Comparative example three: Differences: Fe 3 O 4 was not used to compound with nZVI, reducing the magnetic adsorption capacity.

[0111] Without using carbon nanotubes, the electron transport efficiency decreases, and the degradation rate of organic pollution slows down.

[0112] Without modified attapulgite, the interlayer cation exchange capacity is relatively low, and the heavy metal fixation effect decreases.

[0113] Preparation process: Nano zero-valent iron: FeCl 3 •6H 2 O reacts with NaBH 4 under N 2 protection with stirring at 500 rpm for 30 min, without complexing with Fe 3 O 4 composite.

[0114] Carbon nanotubes: Without adding carbon nanotubes, the electron transport ability decreases.

[0115] Attapulgite modification: Without Na + exchange, directly crushed to 100 nm.

[0116] Pseudomonas aeruginosa powder: Cultured at 37 °C for 48 h, the cells were collected by centrifugation and freeze-dried.

[0117] Mixing and application: Directly mix each component, using the tillage mixing method, applying 3.5 kg per mu.

[0118] Experimental example 1: Experimental purpose: Verify the effect of carbon coating on the antioxidant property and heavy metal removal ability of nano zero-valent iron (nZVI).

[0119] Experimental steps: Reagent and sample preparation: Take Example 1 (carbon-coated nZVI) and Comparative Example 1 (uncoated nZVI), and weigh 0.5 g respectively.

[0120] Expose the two groups of samples to air (relative humidity 50%) respectively for oxidation stability testing.

[0121] Take the same mass of the two kinds of nZVI and add them to 100 mg / L Pb²⁺ solution to evaluate the remediation ability.

[0122] Determination of oxidation rate: Use X-ray photoelectron spectroscopy (XPS) to analyze the change of Fe 0 content, and record the attenuation after 1 h, 6 h, and 24 h.

[0123] Use colorimetry to determine the Fe 2+ concentration, sample at intervals of 1 h, and calculate the Fe 2+ generation rate.

[0124] Removal ability test: Add nZVI of Example 1 and Comparative Example 1 into Pb 2+ solution (100 mg / L) and stir for 2 h.

[0125] Use inductively coupled plasma mass spectrometry (ICP-MS) to measure the residual concentration of Pb 2+ and calculate the removal rate.

[0126] Table 1. Comparison of oxidation rate of nano zero-valent iron and Pb 2+ removal ability Carbon coating effectively reduces the oxidation rate of nZVI. The Fe content in Comparative Example 1 decreased to 40.3% within 6 h, while that in Example 1 remained at 85.7%. This indicates that the carbon layer has a shielding effect on the penetration of oxygen and water, slowing down the oxidation of Fe. The difference in Fe generation rate further confirms this point, and the oxidation rate of Comparative Example 1 is significantly faster. 0 In the Pb removal experiment, the removal rate of Example 1 is always higher than that of Comparative Example 1. After 24 h, the removal rate of uncoated nZVI decreased to 49.6%, while the carbon-coated nZVI could still maintain 67.4%. This is because after the uncoated nZVI is oxidized, the active surface decreases, affecting the heavy metal reduction ability. In contrast, the carbon layer not only prolongs the lifespan of nZVI but also maintains a high electron donor ability. 0 Fe 2+ Overall, the carbon coating technology significantly improves the stability and remediation performance of nZVI. This not only enhances the activity in short-term reactions but also reduces the failure risk in long-term applications, endowing it with better remediation potential in complex environments.

[0127] In the Pb 2+ removal experiment, the removal rate of Example 1 is always higher than that of Comparative Example 1. After 24 h, the removal rate of uncoated nZVI decreased to 49.6%, while the carbon-coated nZVI could still maintain 67.4%. This is because after the uncoated nZVI is oxidized, the active surface decreases, affecting the heavy metal reduction ability. In contrast, the carbon layer not only prolongs the lifespan of nZVI but also maintains a high electron donor ability.

[0128] Overall, the carbon coating technology significantly improves the stability and remediation performance of nZVI. This not only enhances the activity in short-term reactions but also reduces the failure risk in long-term applications, endowing it with better remediation potential in complex environments.

[0129] Experimental Example 2: Experimental purpose: Verify the influence of pH-responsive materials on the stability of soil remediation systems and heavy metal removal ability.

[0130] Experimental steps: Soil sample preparation: Take acidic heavy metal-contaminated soil with pH 4.5 (Cd concentration 200 mg / kg) and divide it into four groups (A, B, C, D). 2+ Group A: Example 2 (containing pH-responsive materials).

[0131] Group A: Example 2 (containing pH-responsive materials).

[0132] Group B: Comparative Example 2 (without adding pH-responsive material).

[0133] Group C: Adding NaOH externally (simulating drastic pH change).

[0134] Group D: Blank control (no treatment).

[0135] Application of the repair agent: For Group A and Group B, 2 kg / m 2 of the repair agent was injected under high pressure and stirred evenly.

[0136] Based on Comparative Example 2, Group C additionally added a NaOH solution (pH 10).

[0137] Index determination: The pH meter was used to continuously monitor for 7 days, and the changes in soil pH were recorded.

[0138] After 7 days, samples were taken to determine the 2+ residual amount of Cd (analyzed by ICP-MS).

[0139] The survival rate of microorganisms was statistically analyzed (plate counting method) to evaluate the impact of the repair agent on the microbial environment.

[0140] Table 2. Comparison of soil pH changes and Cd 2+ removal rate The pH-responsive system effectively regulated the repair environment. The soil pH in Example 2 increased steadily within 7 days and finally stabilized at 7.2. In contrast, Comparative Example 2 remained acidic throughout, and the microbial survival rate was only 35.7%. Although the strong alkaline environment in Group C increased the pH initially, it quickly dropped over time and even fell below the initial value, resulting in a 2+ decrease in the Cd removal rate. This indicates that drastic pH fluctuations are not conducive to stable repair and may disrupt the microbial ecosystem.

[0141] Cd 2+ removal effects showed significant differences. The residual amount of Cd in Example 2 decreased to 43.2 mg / kg, while the removal rate in Comparative Example 2 was less than 50%. This may be related to the impact of pH regulation on the solubility of heavy metals. In a low pH environment, Cd 2+ exists in a free state and is difficult to immobilize. In an appropriate pH range, Cd 2+ can complex or precipitate with the functional groups in the repair material, improving the removal effect. 2+

[0142] The comparison of microbial survival rates further verified the importance of pH stability. In Example 2, the microbial community was maintained, and the final survival rate reached 88.5%. In Group C with drastic fluctuations, the microorganisms almost completely lost their activity. The role of the pH-responsive system lies not only in optimizing the heavy metal removal environment, but also in providing suitable survival conditions for microorganisms, thereby enhancing the long-term stability of the repair system.

[0143] Experimental Example 3: Experimental purpose: To evaluate the effects of slow-release materials (such as sodium alginate and chitosan) on the stable release of the repair agent and its heavy metal removal ability.

[0144] Experimental steps: Preparation of the repair agent: Group A (Example 1): Composite repair agent containing slow-release materials (active components wrapped with sodium alginate + chitosan).

[0145] Group B (Comparative Example 1): The repair agent was directly mixed without using slow-release materials.

[0146] Release rate test: The two groups of repair agents were respectively immersed in simulated groundwater (pH 7.0, 25°C).

[0147] Samples were taken every 12 h, and the release concentration of the active ingredient in the repair agent was measured by ultraviolet spectrophotometry (UV-Vis).

[0148] Monitoring was continued for 7 days to plot the release curve.

[0149] Evaluation of the repair validity period: The two groups of repair agents were respectively applied to Pb 2+ -contaminated soil (Pb 2+ concentration 500 mg / kg) at a dosage of 3 kg / m 2 .

[0150] Samples were taken every 7 days, and the residual amount of Pb 2+ was measured by inductively coupled plasma mass spectrometry (ICP-MS) for 90 days.

[0151] Table 3 Effects of the slow-release system on the release rate of the repair agent and Pb 2+ removal effect The slow-release system significantly delayed the release rate of the repair agent. The release concentration of Group A in the first 24 hours was much lower than that of Group B. This slow release enabled the repair agent to maintain its activity in the environment for a longer time. The repair agent in Group B was released rapidly, showing obvious short-term effects, but the subsequent release tended to saturate. This difference resulted in Group A maintaining a more stable activity throughout the release cycle.

[0152] Pb 2+ The removal rates showed different trends. Group B showed a faster heavy metal removal rate in the early stage (within 72 h), but with the extension of time, the remediation effect gradually weakened. In contrast, Group A showed a more sustained removal ability in the later stage. By 90 days, the 2+ residual amount of Pb was only 48.3 mg / kg, slightly lower than that of Group B. This indicates that the slow-release system contributes more significantly to long-term remediation.

[0153] This phenomenon is closely related to the controlled-release mechanism of the slow-release material. The network structure formed by sodium alginate and chitosan can effectively delay the diffusion of active substances. As the material gradually degrades, the remediation agent is slowly released, thus maintaining a longer reaction time in the soil. It is this slow and continuous release mode that makes Example 1 perform more stably and efficiently in long-term remediation.

[0154] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly additive for soil pollution remediation, characterized in that: Includes the following quality components: 5-20 parts of nano zero-valent iron, 2-15 parts of nano carbon materials, 3-18 parts of nano mineral composite materials; 5-25 parts of biochar, 2-10 parts of microbial flora, 1-10 parts of plant extracts; 1-8 parts of pH responsive material; 2-10 parts of microcapsule material.

2. The environmentally friendly additive for soil pollution remediation according to claim 1, characterized in that: The particle size of the nano zero-valent iron is in the range of 10-100 nm, and the surface is coated with SiO2 or C; The nanocarbon material is selected from activated carbon nanoparticles, graphene, and carbon nanotubes; The nano mineral composite material is prepared by composite modification of montmorillonite, attapulgite, zeolite and iron oxide, and is activated at a high temperature of 300-600°C.

3. The environmentally friendly additive for soil pollution remediation according to claim 1, characterized in that: The microbial flora includes: Heavy metal degrading bacteria: Bacillus subtilis, Pseudomonas, Actinomycetes; Petroleum hydrocarbon degrading bacteria: Pseudomonas petroleum, Aspergillus oryzae; Pollution-resistant actinomycetes: Streptomyces; The microbial flora is cultured by liquid fermentation and can be combined with a biochar carrier.

4. The environmentally friendly additive for soil pollution remediation according to claim 1, characterized in that: The pH responsive material comprises: Polymers: polylactic acid-glycolic acid copolymer, sodium polyacrylate; Inorganic materials: calcium carbonate, magnesium carbonate; Its pH response adjustment range is 5-8, and it accelerates dissolution under low pH conditions, pH ≤ 5.5, and delays release under high pH conditions, pH ≥ 7.

5.

5. The environmentally friendly additive for soil pollution remediation according to claim 1, characterized in that: The microcapsule material is selected from sodium alginate microcapsules, chitosan microcapsules, and starch-based microcapsules, and is used to control the release rate of the pollutant removal core material and the microbial flora, and the release time can reach 30-120 days.

6. A method for applying an environmentally friendly additive for soil pollution remediation, according to the environmentally friendly additive for soil pollution remediation according to any one of claims 1 to 5, characterized in that: The following steps are involved: Contaminant detection: Atomic absorption spectrometry was used to detect heavy metal ions with a detection limit of 0.01 mg / L; Gas chromatography-mass spectrometry was used to detect organic pollutants with a detection limit of 0.001 mg / L; Dosage calculation and preparation: Calculate the required amount of additives based on the test results and mix with appropriate amount of water or carrier to prepare suspension or powder; Heavy metal pollution remediation: spray or mix the additive evenly into the contaminated soil, the applicable pH range is 6.0-8.0; Petroleum hydrocarbon pollution remediation: high pressure injection or tillage mixing method, suitable for soil moisture 30-50%; Pesticide residue pollution remediation: Use surface spreading combined with irrigation infiltration, applicable pH range 5.5-7.5; Mine tailings pond pollution remediation: Spraying, tillage mixing or high-pressure injection are used to evenly distribute additives on the surface and deep soil of the tailings pond; Restoration monitoring: Take samples and analyze the degradation of pollutants every 15-30 days, and adjust the dosage of additives.

7. The method for applying the environmentally friendly additive for soil pollution remediation according to claim 6, characterized in that: Suitable for acidic soil with pH 4.5-6.5, neutral soil with pH 6.5-7.5, and alkaline soil with pH 7.5-8.5; The repair cycles for different pollutants are: heavy metal pollution: 60-180 days; petroleum hydrocarbon pollution: 30-90 days; pesticide pollution: 20-60 days.

8. The method for applying the environmentally friendly additive for soil pollution remediation according to claim 6, characterized in that: After application, pollutant degradation should be regularly tested every 15-30 days; If the pollutant removal rate is less than 50%, adjust the additive formula, including: Increase the amount of nano zero-valent iron or nano mineral composite materials by 10-30%; Adjust the proportion of pH-responsive materials; Re-inoculate the microbial flora.

9. The method for applying the environmentally friendly additive for soil pollution remediation according to claim 6, characterized in that: Application equipment includes spraying equipment, tillage mixing equipment, and high-pressure injection equipment; The suitable application temperature range is 10-35℃, and the suitable soil moisture range is 30-50%.

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