Soil pollution remediation process

Abstract

The invention relates to the technical field of soil remediation, and provides a soil pollution remediation process which comprises the following steps: distributing points in grids of an area to be remediated, measuring the content of heavy metals and the concentration of organic pollutants, applying multi-frequency microwave radiation, synchronously applying ultrasonic treatment, and injecting a complex microbial inoculant containing sphingomonas, aspergillus niger spores and a nitrogen and phosphorus nutrient solution. A direct-current electric field is applied, pH, oxidation-reduction potential Eh and temperature parameters are monitored and measured in real time through an embedded sensor, a repair by-product recovery system is arranged, the purity of recovered metal is not lower than 98%, and mobile repair equipment is used in a matched mode. According to the method, the pollution degree is accurately quantified by constructing the pollution index PI, and dynamic regulation and repair are realized in combination with real-time monitoring parameters of a sensor. The pollutant removal efficiency is improved through the synergistic effect of multiple technologies, metal resource recovery is achieved through a repair by-product recovery system, traditional problems are solved, and efficient and environment-friendly repair is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a soil pollution remediation process. Background Art

[0002] In existing soil pollution remediation technologies, pollution monitoring often uses simple single-point sampling or only detects a few indicators. There is no comprehensive system to accurately quantify the degree of pollution. The remediation process often relies on a single technology, such as removing heavy metals only through physical adsorption or relying on ordinary microorganisms for biological remediation. The processing capacity is insufficient when faced with complex pollution where heavy metals and organic pollutants coexist; process control often follows fixed processes and parameters, and lacks dynamic monitoring and flexible regulation of soil parameters, making it difficult to fully and accurately reflect the soil pollution status. The remediation work lacks specificity, the treatment effect on complex pollution is poor, and the remediation strategy cannot be adjusted in time according to the actual soil conditions, which ultimately leads to low remediation efficiency and difficulty in ensuring the effect. It may also cause waste of resources and cannot meet the needs of efficient and accurate modern soil pollution remediation. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention provides a soil pollution remediation process, which solves the problems of inaccurate pollution monitoring, reliance on a single technology for remediation, lack of dynamic monitoring and flexible regulation in process control, resulting in low remediation efficiency, poor results and waste of resources in traditional soil pollution remediation technology.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions: A soil contamination remediation process comprises the following steps: S1. Three-dimensional positioning of pollution: Using an X-ray fluorescence spectrometer combined with a gas chromatography detection device, the heavy metal content is measured in the area to be repaired according to a 0.5m×0.5m grid. and organic pollutant concentrations The units of both are mg / kg, and the pollution index is constructed ,in, is the benchmark value of heavy metal content, is the heavy metal pollution weight coefficient, is the base value of organic pollutant concentration, which is 100 mg / kg. is the pollution weight coefficient of organic pollutants; S2. Microwave-ultrasonic pretreatment: Multi-frequency microwave radiation was applied to the area with a frequency range of 300MHz-5GHz, and the soil temperature was controlled to rise to 85±5℃ and maintained for 15min. The frequency was 40kHz and the power density was 0.8W / cm 2 Ultrasonic treatment; S3. Injection of compound microbial agent: Calculate the amount of bacterial solution injected, where The volume of bacterial solution injected, in L; is the polluted area, in m 2 ; is the pollution depth, in m; is the coefficient of soil bacterial solution injection per unit volume. The bacterial agent contains Sphingomonas, Aspergillus niger spores and nitrogen and phosphorus nutrient solution. The OD of the Sphingomonas 600 The value is 1.2, and the concentration of Aspergillus niger spores is 10 6 CFU / g, the carbon, nitrogen and phosphorus ratio of the nitrogen and phosphorus nutrient solution is 25:5:1; S4. Electrokinetic Enhanced Migration: A DC electric field was applied with a gradient voltage range of 1-3 V / cm. A 0.1 mol / L citric acid solution was injected into the cathode region. An ion exchange membrane was installed in the anode region. The current density was controlled at 5 mA / cm. 2 ; S5. Dynamic control: Real-time monitoring of pH, redox potential (Eh), and temperature parameters is achieved through embedded sensors. When the pH value is detected to be less than 5.5, the alkali solution automatic replenishment system is activated. When the redox potential (Eh) is greater than 400mV, the reducing agent injection device is triggered. When the temperature deviates from the set value by ±3°C, the microwave power is adjusted.

[0005] Preferably, the microwave radiation described in S2 adopts a three-band alternating irradiation mode: first irradiate at a frequency of 2.45 GHz for 5 minutes, switch to a frequency of 915 MHz for 7 minutes, and finally irradiate at a frequency of 5.8 GHz for 3 minutes, with the power density of each frequency band being 1.5 W / cm 2 , 2.2W / cm 2 , 0.8W / cm 2 .

[0006] Preferably, the composite bacterial agent described in S3 adopts microcapsule coating technology, the capsule wall is a sodium alginate-chitosan double-layer structure, the thickness range is 80-120 μm, the capsule core contains 0.5% slow-release biostimulant, and the bacterial agent is continuously released in the soil for 20-35 days.

[0007] Preferably, the electric field in S4 is applied in an asymmetric pulse mode, with a positive pulse width of 10 ms, a negative pulse width of 5 ms, and a pulse frequency of ,in The number of days for repair The frequency of the day is automatically adjusted to .

[0008] Preferably, in S5, a fuzzy PID control algorithm is used to adjust the processing parameters and establish a control model: , in, , is the temperature setting value With actual value The deviation, is the proportionality coefficient; is the integration coefficient; is the differential coefficient; The microwave power adjustment value is in W, and the control period is 5 minutes.

[0009] Preferably, the acceptance criteria after repair must meet the following requirements: Heavy metal stabilization rate ,in The heavy metal content after repair, is the heavy metal content before restoration; Degradation rate of organic pollutants ,in is the concentration of organic pollutants after remediation, is the concentration of organic pollutants before remediation.

[0010] Ecotoxicity index EC 50 Not less than 500mg / kg, using the luminescent bacteria toxicity test method.

[0011] Preferably, a repair by-product recovery system is also provided: a heavy metal deposition electrode is installed in the cathode area of the electric field, and the electrode adopts a titanium-based platinum-plated mesh structure. When the deposition amount on the electrode surface reaches 1.2g / cm 2 The electrode is automatically replaced when the machine is running, and the purity of recovered metal is not less than 98%.

[0012] Preferably, it also includes the use of mobile repair equipment, which integrates a microwave transmitter, a high-pressure injection system for bacterial agents and a multi-parameter detection module, and the overall size of the equipment does not exceed 2m×1.5m×1.2m.

[0013] The present invention provides a soil contamination remediation process. It has the following beneficial effects: 1. The present invention accurately quantifies the degree of pollution by constructing a pollution index (PI). It combines embedded sensors to monitor parameters such as pH, redox potential (Eh), and temperature in real time, and dynamically regulates alkali solution replenishment, reducing agent injection, and microwave power. This achieves precise positioning of contaminated areas and intelligent adjustment of the remediation process, avoiding blind remediation and significantly improving remediation efficiency and effectiveness.

[0014] 2. The present invention uses the synergistic effects of microwave-ultrasonic pretreatment, composite bacterial agent injection, and electric enhanced migration. Microwave ultrasound destroys the structure of pollutants and increases the temperature, promoting subsequent bacterial agent degradation and electric migration; the composite bacterial agent efficiently decomposes pollutants according to their characteristics; and the electric enhanced migration uses the electric field to drive the directional movement of pollutants, greatly improving the efficiency of pollutant removal. At the same time, the repair by-product recovery system realizes the efficient recovery of metal resources, solving the problems of low efficiency and resource waste of traditional single technology repair, and realizing efficient and environmentally friendly repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] Example: Please see the attached Figure 1 , an embodiment of the present invention provides a soil contamination remediation process, comprising the following steps: S1. Three-dimensional positioning of pollution: Using an X-ray fluorescence spectrometer combined with a gas chromatography detection device, the heavy metal content is measured in the area to be repaired according to a 0.5m×0.5m grid. and organic pollutant concentrations , both units are mg / kg, to construct the pollution index ,in, is the benchmark value of heavy metal content, is the heavy metal pollution weight coefficient, is the baseline value of organic pollutant concentration, is the pollution weight coefficient of organic pollutants, among which the baseline value of heavy metal content =80mg / kg, heavy metal pollution weight coefficient =0.6, organic pollutant concentration baseline value =100mg / kg, organic pollutant pollution weight coefficient =0.4. Through gridded detection and multi-instrument testing, the spatial distribution characteristics of soil pollution can be accurately obtained. A pollution index model combining logarithmic and power functions takes into account the cumulative effects of heavy metals while highlighting the nonlinear toxicity characteristics of organic pollutants. The weight coefficient reflects the dominant position of heavy metals in this type of contaminated soil, enabling the pollution index to more accurately reflect the actual degree of pollution and provide a precise basis for subsequent remediation.

[0018] S2. Microwave-ultrasonic pretreatment: Multi-frequency microwave radiation was applied to the area, using a three-band alternating irradiation mode: first, the frequency was 2.45 GHz and the power density was 1.5 W / cm 2 Irradiate for 5 minutes, then switch to a frequency of 915 MHz and a power density of 2.2 W / cm 2 Irradiate for 7 minutes, and finally use a frequency of 5.8 GHz and a power density of 0.8 W / cm 2 Irradiate for 3 minutes, control the soil temperature to 85℃ and maintain it for 15 minutes, and simultaneously apply a frequency of 40kHz and a power density of 0.8W / cm 2 Ultrasonic treatment. 2.45GHz microwaves can effectively penetrate the soil, stimulating polar molecules to vibrate and generate heat; 915MHz microwaves can penetrate deep into the soil to promote the thermal desorption of organic pollutants; 5.8GHz microwaves strengthen collisions between molecules and accelerate the decomposition of pollutants. Alternating irradiation of the three frequency bands can avoid the "hot spot" effect caused by a single frequency, allowing the soil temperature to rise evenly. The microjets and shock waves generated by the cavitation effect of 40kHz ultrasound can destroy the agglomeration structure of soil particles and increase the mobility of pollutants. This combined treatment increases the desorption rate of polycyclic aromatic hydrocarbons in the soil to 87%, creating favorable conditions for subsequent remediation.

[0019] S3. Compound bacterial agent injection Calculate the amount of bacterial solution injected, V is the volume of bacterial solution injected, unit is L; A is the contaminated area, unit is m 2 ; D is the pollution depth, unit is m; unit volume soil bacterial solution injection coefficient =0.08, the bacterial agent contains OD 600 Sphingomonas with a value of 1.2 and a concentration of 10 6 The composite microbial agent utilizes microencapsulation technology, with a sodium alginate-chitosan double-layer structure and a 100μm-thick capsule wall. The capsule core contains 0.5% sustained-release biostimulant, and the agent maintains a sustained release period of 28 days in the soil. The highly efficient degradation of polycyclic aromatic hydrocarbons by Sphingomonas and the exoenzymes secreted by Aspergillus niger spores can break down complex organic matter. The synergistic effect of these two agents expands the degradation spectrum. The 25:5:1 carbon, nitrogen, and phosphorus ratio meets the metabolic needs of microorganisms in this type of contaminated soil, promoting their growth and reproduction. The 100μm-thick double-layer microcapsule structure resists physical stress in the soil while allowing for the slow release of the agent through diffusion. The 28-day sustained release period matches the biodegradation cycle of pollutants, effectively improving degradation efficiency.

[0020] S4. Electrokinetic enhanced migration was performed by applying a DC electric field with a gradient voltage of 2 V / cm. A citric acid solution with a concentration of 0.1 mol / L was injected into the cathode region. An ion exchange membrane was set up in the anode region. The current density was controlled at 5 mA / cm2. The electric field was applied in an asymmetric pulse mode with a positive pulse width of 10 ms, a negative pulse width of 5 ms, and a pulse frequency of , where n is the number of repair days, and the frequency is automatically adjusted to The 2V / cm gradient voltage ensures the efficiency of ion migration while avoiding the damage to the soil structure caused by excessive voltage. Citric acid, as a chelating agent, can form stable complexes with heavy metals and improve their mobility. The ion exchange membrane can prevent the hydroxide ions generated in the cathode area from migrating to the anode, avoiding the precipitation of heavy metal hydroxides. In the asymmetric pulse mode, the positive pulse promotes the migration of cations, and the negative pulse alleviates the electrode polarization phenomenon. The design of increasing frequency with the number of repair days adapts to the process of gradually decreasing pollutant concentration and improves the migration efficiency of heavy metals.

[0021] S5. Dynamically controlled alkali solution automatic replenishment system: An embedded sensor monitors pH in real time. When the pH value is detected to be less than 5.5, the alkali solution automatic replenishment system is activated. The system consists of an alkali solution storage tank, a pH sensor, a controller, and an infusion pump. The pH sensor transmits the detected pH value signal to the controller, which compares it with the set value of 5.5. When the pH value is less than 5.5, the controller issues a command to the infusion pump, which draws an appropriate amount of 0.2 mol / L sodium hydroxide solution from the alkali solution storage tank and injects it into the soil through a pipe laid in the soil to adjust the soil pH. Reducing agent injection device: An embedded sensor monitors the redox potential (Eh) in real time. When Eh exceeds 400 mV, the reducing agent injection device is activated. The device mainly comprises a reducing agent storage tank, a pressure pump, a spray nozzle, and a control unit. Upon receiving the signal from the Eh sensor, the control unit controls the pressure pump to pump 0.3 mol / L sodium sulfite solution from the storage tank and transport it through a pipe to the spray nozzle installed on the soil surface, where the reducing agent is injected into the soil to lower the soil's redox potential. Temperature regulation: When the temperature deviates from the set value by 85℃, the fuzzy PID control algorithm is used to adjust the processing parameters. Establish the control model: ,in, , is the deviation between the temperature setting value and the actual value, the proportional coefficient =0.7; integral coefficient =0.03; differential coefficient =0.15; is the microwave power adjustment value, the unit is W, the control cycle is 5 minutes, and the soil temperature is controlled by adjusting the microwave power. Alkali automatic supply system: 0.2mol / L sodium hydroxide solution can not only effectively increase the soil pH value, but also avoid soil compaction caused by local high alkalinity. Maintaining the pH value above 5.5 can promote the metabolic activity of microorganisms and inhibit the dissolution of heavy metals. Reducing agent injection device: 0.3mol / L sodium sulfite solution can quickly reduce the redox potential of the soil, reducing high-valent heavy metals to low-toxic low-valent states, reducing their mobility and biotoxicity. Temperature regulation: The parameter combination in the fuzzy PID control algorithm gives the temperature control system good response speed and stability. The 5-minute control cycle can adjust the temperature in a timely manner and avoid the increase in energy consumption caused by frequent adjustments, accurately controlling the soil temperature within the range of 85℃±0.5℃.

[0022] After restoration, the heavy metal stabilization rate meets the requirements ,in The heavy metal content after repair, is the heavy metal content before remediation. The degradation rate of organic pollutants meets ,in is the concentration of organic pollutants after remediation, The concentration of organic pollutants before remediation. Ecotoxicity index: The ecotoxicity index EC is tested using the luminescent bacteria toxicity test method. 50 The specific test method is as follows: select Vibrio fischeri as the test bacteria, mix the repaired soil extract with luminous bacteria in a ratio of 1:10, culture at 20℃ for 15 minutes, use a photometer to measure the luminous intensity of the luminous bacteria, and compare it with the blank control group, and calculate the EC according to the change in luminous intensity. 50 The heavy metal stabilization rate reached over 92%, indicating that most heavy metals were fixed in the soil, reducing their bioavailability and mobility. The organic pollutant degradation rate was over 88%, indicating that most organic pollutants were decomposed into harmless substances. 50 The value is 550 mg / kg, indicating that the ecotoxicity of the repaired soil is significantly reduced and meets the soil environmental quality standards. This acceptance system comprehensively evaluates the repair effect from both chemical and ecological perspectives to ensure that the repaired soil meets the requirements for safe utilization.

[0023] Repair byproduct recovery: A heavy metal deposition electrode is installed in the cathode area of the electric field. The electrode adopts a titanium-based platinum-plated mesh structure. When the deposition amount on the electrode surface reaches 1.2g / cm², the electrode is automatically replaced. The purity of the recovered metal is not less than 98%. The titanium-based platinum-plated mesh structure electrode has good conductivity and corrosion resistance, and can effectively capture heavy metal ions that migrate to the cathode. 1.2g / cm² 2The deposition amount setting not only ensures the recovery efficiency of the electrode, but also avoids the increase in resistance caused by too thick a deposition layer. The purity of the recovered metal is not less than 98%, and it can directly enter the metal smelting process, realizing the recycling of resources, reducing repair costs and reducing secondary pollution.

[0024] The overall size of the mobile repair equipment is 1.8m×1.2m×1.0m, and it integrates the following modules: Microwave transmitter: It can transmit microwaves with a frequency of 2.45GHz and a power density of 1.5W / cm 2 The system automatically adjusts its operating time based on soil temperature feedback. The high-pressure microbial injection system includes a high-pressure pump, a microbial storage tank, and an injection nozzle. The high-pressure pump injects the composite microbial agent from the microbial storage tank into the soil at a pressure of 8 MPa through the injection nozzle. The fan-shaped injection nozzle has a 60° spray angle and can cover an area with a diameter of 2 meters. The multi-parameter detection module integrates a pH sensor, an oxidation-reduction potential (Eh) sensor, a temperature sensor, a heavy metal content sensor, and an organic pollutant concentration sensor. It collects soil pH, Eh, temperature, heavy metal content, and organic pollutant concentration data in real time and transmits this data to a control terminal via a 4G network, allowing operators to promptly monitor soil remediation status and adjust remediation parameters. This enables remote monitoring and intelligent control, improving remediation efficiency and accuracy.

[0025] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A soil pollution remediation process, characterized in that: The following steps are involved: S1. Three-dimensional positioning of pollution: Using an X-ray fluorescence spectrometer combined with a gas chromatography detection device, the heavy metal content is measured in the area to be repaired according to a 0.5m×0.5m grid. and organic pollutant concentrations , both units are mg / kg, to construct the pollution index ,in, is the benchmark value of heavy metal content, is the heavy metal pollution weight coefficient, is the baseline value of organic pollutant concentration, is the pollution weight coefficient of organic pollutants; S2. Microwave-ultrasonic pretreatment: Multi-frequency microwave radiation was applied to the area with a frequency range of 300MHz-5GHz, and the soil temperature was controlled to rise to 85±5℃ and maintained for 15min. The frequency was 40kHz and the power density was 0.8W / cm 2 Ultrasonic treatment; S3. Injection of compound microbial agent: Calculate the amount of bacterial solution injected, where The volume of bacterial solution injected, in L; is the polluted area, in m 2 ; is the pollution depth, in m; is the coefficient of soil bacterial solution injection per unit volume. The bacterial agent contains Sphingomonas, Aspergillus niger spores and nitrogen and phosphorus nutrient solution. The OD of the Sphingomonas 600 The value is 1.2, and the concentration of Aspergillus niger spores is 10 6 CFU / g, the carbon, nitrogen and phosphorus ratio of the nitrogen and phosphorus nutrient solution is 25:5:1; S4. Electrokinetic Enhanced Migration: A DC electric field was applied with a gradient voltage range of 1-3 V / cm. A 0.1 mol / L citric acid solution was injected into the cathode region. An ion exchange membrane was installed in the anode region. The current density was controlled at 5 mA / cm. 2 ; S5. Dynamic control: Real-time monitoring of pH, redox potential (Eh), and temperature parameters is achieved through embedded sensors. When the pH value is detected to be less than 5.5, the alkali solution automatic replenishment system is activated. When the redox potential (Eh) is greater than 400mV, the reducing agent injection device is triggered. When the temperature deviates from the set value by ±3°C, the microwave power is adjusted.

2. A soil contamination remediation process according to claim 1, characterized in that: The microwave radiation described in S2 adopts a three-band alternating irradiation mode: first irradiate at a frequency of 2.45 GHz for 5 minutes, switch to a frequency of 915 MHz for 7 minutes, and finally irradiate at a frequency of 5.8 GHz for 3 minutes. The power density of each frequency band is 1.5 W / cm 2 , 2.2W / cm 2 , 0.8W / cm 2 .

3. A soil contamination remediation process according to claim 1, characterized in that: The composite bacterial agent described in S3 adopts microcapsule coating technology. The capsule wall is a double-layer structure of sodium alginate and chitosan with a thickness ranging from 80 to 120 μm. The capsule core contains 0.5% slow-release biostimulant. The bacterial agent is continuously released in the soil for 20 to 35 days.

4. A soil contamination remediation process according to claim 1, characterized in that: The electric field application in S4 adopts an asymmetric pulse mode, with a positive pulse width of 10ms, a negative pulse width of 5ms, and a pulse frequency of ,in The number of days for repair The frequency of the day is automatically adjusted to .

5. A soil contamination remediation process according to claim 1, characterized in that: In S5, fuzzy PID control algorithm is used to adjust processing parameters and establish a control model: ， in, , is the temperature setting value With actual value The deviation, is the proportionality coefficient; is the integration coefficient; is the differential coefficient; The microwave power adjustment value is in W, and the control period is 5 minutes.

6. A soil contamination remediation process according to claim 1, characterized in that: The acceptance criteria after repair must meet the following requirements: Heavy metal stabilization rate ,in The heavy metal content after repair, is the heavy metal content before restoration; Degradation rate of organic pollutants ,in is the concentration of organic pollutants after remediation, is the concentration of organic pollutants before remediation.

7. Ecotoxicity index EC 50 Not less than 500mg / kg, using the luminescent bacteria toxicity test method.

8. A soil contamination remediation process according to claim 1, characterized in that: The system also includes the installation of a repair by-product recovery system: a heavy metal deposition electrode is installed in the cathode area of the electric field. The electrode adopts a titanium-based platinum-plated mesh structure. When the deposition amount on the electrode surface reaches 1.2g / cm 2 The electrode is automatically replaced when the machine is running, and the purity of recovered metal is not less than 98%.

9. A soil contamination remediation process according to claim 1, characterized in that: It also includes the use of mobile repair equipment, which integrates a microwave transmitter, a high-pressure injection system for bacterial agents, and a multi-parameter detection module. The overall size of the equipment does not exceed 2m×1.5m×1.2m.

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