A multi-stage collaborative leaching remediation system for composite contaminated soil

Abstract

The application discloses a kind of composite contaminated soil multistage collaborative leaching repair systems, belong to soil repair technical field.The device includes: feed device, for transporting contaminated soil and carrying out preliminary crushing;Classification screening device, at least three screening equipment is included, and soil is divided into coarse particle, medium particle, fine particle three according to particle size;Multi-stage leaching device, particle size-pollutant-leaching agent three precision matching mechanism, first establish the quantitative correlation model of " particle size-pollutant (heavy metal) form-leaching agent formula", realize accurate target cleaning.Compound leaching agent adjusting device, including a variety of leaching agent storage unit, detection unit and adjusting unit, real-time monitoring and adjusting the type, concentration and pH of leaching agent;Leaching solution recycling device, including flocculation precipitation unit, oxidation regeneration unit and concentration adjusting unit, leaching solution regeneration-circulation four-stage advanced treatment technology, first " flocculation-high level oxidation-concentration regeneration " three-stage regeneration process, break leaching solution secondary pollution bottleneck.The application can solve the two major pain points of the industry at present, and the removal efficiency of fine particle pollution is low, and the special strong chelation-reducing agent leaching unit is aimed at high adsorptive soil;High repair cost / secondary pollution, leaching solution deep regeneration and near-zero discharge recycling.

Description

Technical Field

[0001] This invention relates to the field of soil remediation devices, specifically to a multi-stage synergistic leaching remediation system for complex contaminated soil. Background Technology

[0002] With the acceleration of industrialization, the problem of complex soil pollution is becoming increasingly serious, especially the remediation of soils contaminated with both heavy metals and organic matter. Currently, chemical leaching technology has become an important method for the remediation of complex polluted soils due to its advantages such as high treatment efficiency and short cycle time. However, traditional leaching technology faces many technical bottlenecks when treating soils of different particle sizes and complex pollutants.

[0003] In the prior art, WO2018006708A1 discloses an ex-situ chemical leaching remediation device for heavy metal contaminated soil and a washing liquid reuse device. This device includes a dry drum screen, a grinder, a wet drum screen, a primary leaching reaction tank, a secondary leaching reaction tank, and a washing liquid reuse device. While this technology achieves the recycling of the washing liquid, it primarily targets heavy metal pollution and has limited effectiveness in treating combined organic and heavy metal pollution.

[0004] CN104525556B proposes a mobile device and method for leaching composite contaminated soil. The device includes a multi-stage screening and leaching system, a fine-particle stirring and washing system, a coarse-particle cyclone washing system, and a large-particle spiral washing system, all housed within a casing. While this device considers the graded treatment of soils with different particle sizes, the leaching agent formulation is singular, making it difficult to optimize and adjust it to suit the characteristics of pollutants in soils of different particle sizes.

[0005] In summary, the existing technology has the following shortcomings: 1. Existing leaching technologies mostly use a single leaching agent, which makes it difficult to effectively treat soils with combined heavy metal and organic pollution at the same time, especially the synergistic removal effect of different types of pollutants is not good; 2. Although the existing equipment takes into account soil grading and screening, it lacks a matching multi-stage rinsing unit, which makes it impossible to treat the adsorption characteristics of pollutants in soils of different particle sizes in a targeted manner. Summary of the Invention

[0006] To address the technical challenges of using a single leaching agent to effectively treat soils contaminated with both heavy metals and organic matter, the varying adsorption capacities of soils with different particle sizes requiring targeted treatment, the high cost of leaching solutions and the risk of secondary pollution, and the significant differences in leaching effects due to variations in soil type, a multi-stage synergistic leaching remediation system for contaminated soils is proposed.

[0007] The technical solution adopted by the present invention to solve its technical problem is: to provide a multi-stage synergistic leaching remediation system for composite contaminated soil, including a feeding device, a grading and screening device, a multi-stage leaching device, a compound leaching agent adjustment device, and a leaching liquid circulation and regeneration device. The system includes a feeding device for conveying contaminated soil and performing preliminary crushing; a grading and screening device comprising at least three stages of screening equipment for separating the pre-crushed soil into at least three grades: coarse, medium, and fine particles; a multi-stage leaching device with at least three leaching units matching the grading and screening levels of the grading and screening device, each leaching unit being used to specifically leach soil of different particle sizes; a compound leaching agent adjustment device comprising multiple leaching agent storage units, a detection unit, and an adjustment unit, wherein the detection unit is used to monitor the concentration of pollutants and pH value in the leaching solution in real time, and the adjustment unit, based on the monitoring results of the detection unit, adjusts the type, concentration, and pH value of the leaching agent and delivers it to the multi-stage leaching device; and a leaching solution recycling and regeneration device comprising a flocculation and sedimentation unit, an oxidation regeneration unit, and a concentration adjustment unit connected in sequence, wherein the flocculation and sedimentation unit is used to remove heavy metal precipitates from the leaching solution, the oxidation regeneration unit is used to degrade organic matter in the leaching solution, and the concentration adjustment unit is used to adjust the concentration of the regenerated leaching solution for recycling to the multi-stage leaching device.

[0008] A further preferred embodiment of the present invention is: the three-stage screening equipment of the grading and screening device includes a drum screen, a hydrocyclone and a vibrating screen; wherein, the drum screen is used to screen out coarse soil particles with a particle size greater than 2 mm, the hydrocyclone is used to screen medium soil particles with a particle size of 0.15-2 mm, and the vibrating screen is used to screen fine soil particles with a particle size less than 0.15 mm.

[0009] A further preferred embodiment of the present invention is: in the three-stage rinsing unit of the multi-stage rinsing device: a three-stage precise matching mechanism of particle size, pollutants, and rinsing agent, and innovative graded screening: through a three-stage sieving process of drum screen (>2mm), hydrocyclone (0.15-2mm), and vibrating screen (<0.15mm), the soil is precisely separated according to the adsorption characteristics of pollutants (coarse particles: low adsorption; fine particles: high adsorption).

[0010] Dynamic rinsing strategy: Coarse particles: Rinsing with clean water / low acid (pH 2.0-3.0) → Low-cost dissociation of surface-adsorbed pollutants; Medium particles: Chelating agent + surfactant (pH 5.5-6.5) → Simultaneous removal of heavy metals and organic matter; Fine particles: Strong chelating agent + reducing agent (pH 2.5-3.5) → Breaking down organic matter-bound metals. Breakthrough: The first establishment of a quantitative correlation model of "particle size - pollutant (heavy metal) morphology - rinsing agent formulation" to achieve precise targeted cleaning.

[0011] A further preferred embodiment of the present invention is that the rinsing agent storage unit of the compound rinsing agent conditioning device includes a chelating agent, a surfactant, a reducing agent, and an oxidizing agent; wherein the chelating agent is selected from ethylenediaminetetraacetic acid or sodium N-dodecylethylenediaminetriacetate, the surfactant is selected from rhamnolipid or saponins, the reducing agent is selected from ascorbic acid or sodium oxalate, and the oxidizing agent is selected from persulfate or ozone.

[0012] A further preferred embodiment of the present invention is that the regulating unit of the compound leaching agent regulating device adopts an "oxidation first, leaching later" strategy for compound contaminated soil: first, the organic matter in the soil is decomposed by the oxidant, and then the heavy metals and residual organic matter are simultaneously leached by the compound solution of chelating agent and surfactant.

[0013] A further preferred embodiment of the present invention is: the flocculation and sedimentation unit of the rinsing fluid circulation replenishment device adds polyaluminum chloride and polyacrylamide for coagulation and sedimentation, and controls the pH value to be 7-8; wherein, the amount of PAC added is 0.1%, and the amount of PAM added is 0.01%.

[0014] A further preferred embodiment of the present invention is that the oxidation regeneration unit of the rinsing solution circulation replenishment device adopts ozone / persulfate synergistic oxidation technology, controlling the ozone dosage to be 0.7-0.8 kg / kg chemical oxygen demand, the sodium persulfate concentration to be 4000-5000 mg / L, the pH value to be 8.5-9.5, and the reaction time to be 180-240 minutes.

[0015] A further preferred embodiment of the present invention is that the concentration adjustment unit of the rinsing fluid circulation and regeneration device is a rinsing fluid generator, and the rinsing fluid generator controls the concentration of the rinsing fluid by means of current and mother liquor flow rate, wherein the mother liquor includes potassium hydroxide solution, sodium hydroxide solution or ethylenediaminetetraacetic acid solution.

[0016] A further preferred embodiment of the present invention is: a four-stage deep treatment technology for eluent regeneration and circulation; flocculation and sedimentation: PAC+PAM coagulation (pH 7-8) → removing 99% of heavy metal precipitates; oxidative regeneration: O3 / persulfate synergistic oxidation (COD removal rate ≥90%) → degrading organic toxins; concentration adjustment: electrochemical eluent generator → precisely controlling the regenerated liquid concentration through current / mother liquor flow rate; closed-loop circulation: regenerated liquid reuse rate ≥80%, reducing reagent costs by more than 50%, and achieving near-zero emissions. Breakthrough: The pioneering "flocculation-advanced oxidation-concentration regeneration" three-stage regeneration process overcomes the bottleneck of secondary pollution in eluents.

[0017] A further preferred embodiment of the present invention is that the control system is a distributed control system, a distributed electronic control system, and integrates a 5G cloud IoT module to realize real-time monitoring, automatic adjustment and remote management of equipment operating parameters.

[0018] The beneficial effects of this invention are as follows: Through a graded screening and leaching linkage system, precise treatment is achieved for soils of different particle sizes, improving pollutant removal efficiency; the dynamic adjustment device for compound leaching agents automatically selects appropriate leaching agent combinations and concentrations based on the type of pollutant, ensuring optimal leaching results; the leaching liquid recycling system achieves a recycling rate of over 80%, significantly reducing leaching agent consumption and wastewater treatment costs; it avoids the risk of secondary pollution from the leaching liquid, improving environmental friendliness; and the modular integrated design makes the device easy to operate, highly adaptable, and applicable to the remediation of different types of compound contaminated soils. Compared with existing technologies, this invention can simultaneously and effectively treat soils contaminated with both heavy metals and organic matter, solving the problem of poor treatment effects with a single leaching agent, and addressing the technical challenge of significant differences in leaching effects for soils of different particle sizes through graded treatment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the multi-stage synergistic leaching remediation device for composite contaminated soil in the embodiments of this application; Figure 2 This is a schematic diagram of the compound rinsing agent adjustment device in the embodiments of this application; Figure 3 This is a schematic diagram of the three-stage screening equipment in the embodiments of this application. Detailed Implementation

[0020] 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 some embodiments of the present invention, and not all embodiments. 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.

[0021] Example: Figure 1-3 As shown, a multi-stage synergistic leaching remediation system for complex contaminated soil includes a feeding device, a grading and screening device, a multi-stage leaching device, a compound leaching agent adjustment device, a leaching liquid circulation and regeneration device, and a control system.

[0022] The feeding device is used to transport contaminated soil and perform preliminary crushing. The contaminated soil is transported into the device through the feeding device, where it undergoes preliminary crushing to make the soil particles easier to screen and wash later.

[0023] The grading and screening device comprises three stages of screening equipment: a drum screen, a hydrocyclone, and a vibrating screen. The drum screen removes coarse soil particles larger than 2 mm, the hydrocyclone separates medium-sized soil particles (0.15-2 mm), and the vibrating screen separates fine soil particles smaller than 0.15 mm. This three-stage screening design accurately separates the initially crushed soil into coarse, medium, and fine particle sizes, providing a foundation for subsequent targeted leaching.

[0024] The multi-stage leaching device is equipped with three leaching units matched to the screening levels of the grading and screening device, each specifically designed for leaching soil particles of different sizes. For coarse-grained soils, the leaching unit uses clean water or a low-concentration acidic leaching agent, controlling the pH at 2.0-3.0, the liquid-to-solid ratio at 1:4-1:6, and the treatment time at 1-3 hours. For medium-grained soils, the leaching unit uses a compound leaching agent of chelating agents and surfactants, controlling the pH at 5.5-6.5, the liquid-to-solid ratio at 1:2-1:4, and the treatment time at 3-5 hours. For fine-grained soils, the leaching unit uses a compound leaching agent of strong chelating agents and reducing agents, controlling the pH at 2.5-3.5, the liquid-to-solid ratio at 1:1-1:3, and the treatment time at 5-7 hours. This tiered leaching method can precisely treat soils of different particle sizes based on their pollution characteristics, improving leaching efficiency.

[0025] The compound leaching agent conditioning device includes multiple leaching agent storage units, detection units, and conditioning units. The leaching agent storage unit includes an acidic leaching agent, a chelating agent, a surfactant, a reducing agent, and an oxidizing agent. Specifically, the acidic leaching agent is selected from sulfuric acid or phosphoric acid; the chelating agent is selected from ethylenediaminetetraacetic acid or sodium N-dodecylethylenediaminetriacetate; the surfactant is selected from rhamnolipids or saponins; the reducing agent is selected from ascorbic acid or sodium oxalate; and the oxidizing agent is selected from persulfate or ozone. The detection unit monitors the pollutant concentration and pH value in the leaching solution in real time. Based on the monitoring results, the conditioning unit adjusts the type, concentration, and pH value of the leaching agent and delivers it to the multi-stage leaching unit. For complex contaminated soils, the conditioning unit adopts a "pre-oxidation followed by leaching" strategy: first, the organic matter in the soil is decomposed by the oxidizing agent, and then heavy metals and residual organic matter are simultaneously leached by a compound solution of the chelating agent and surfactant. This intelligent conditioning system can optimize the leaching agent formulation in real time according to the characteristics of the pollutants, improving treatment efficiency.

[0026] The eluent circulation and regeneration device comprises a flocculation and sedimentation unit, an oxidation regeneration unit, and a concentration adjustment unit connected in sequence. The flocculation and sedimentation unit adds polyaluminum chloride (PAC) and polyacrylamide (PAM) for coagulation and sedimentation, controlling the pH to 7-8; the addition amount of PAC is 0.1%, and the addition amount of PAM is 0.01%. The flocculation and sedimentation unit is used to remove heavy metal precipitates from the eluent. The oxidation regeneration unit employs ozone / persulfate synergistic oxidation technology, controlling the ozone dosage at 0.7-0.8 kg / kg COD, the sodium persulfate concentration at 4000-5000 mg / L, the pH at 8.5-9.5, and the reaction time at 180-240 minutes. The oxidation regeneration unit is used to degrade organic matter in the eluent. The concentration adjustment unit is an eluent generator, which controls the eluent concentration by controlling the current and mother liquor flow rate. The mother liquor includes potassium hydroxide solution, sodium hydroxide solution, or ethylenediaminetetraacetic acid (EDTA) solution. The concentration adjustment unit is used to adjust the concentration of the regenerated eluent for circulation to the multi-stage eluent system. This recycling system significantly reduces the consumption of rinsing agents and waste liquid discharge, achieving resource recycling.

[0027] The grading and screening device and the multi-stage leaching device form a closed-loop linkage through a control system. The screened soil automatically enters the corresponding leaching unit, and the leaching solution circulates between the multi-stage leaching device and the leaching solution recycling and regeneration device via pipelines. The control system is a distributed electronic control system (DAS) and integrates a 5G cloud IoT module for real-time monitoring, automatic adjustment, and remote management of equipment operating parameters. This intelligent control system achieves fully automated operation, improving processing efficiency and stability.

[0028] This multi-stage synergistic leaching remediation device for complex contaminated soil achieves precise treatment of soil with different particle sizes through a combination of graded screening and targeted leaching. Its intelligent leaching agent formulation and recycling system reduces treatment costs and minimizes secondary pollution. Full-process automated control improves treatment efficiency and stability. This device is particularly suitable for the remediation of soils contaminated with both heavy metals and organic matter, offering advantages such as high treatment efficiency, low resource consumption, and environmental friendliness.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 multi-stage synergistic leaching remediation system for composite contaminated soil, characterized in that, include: A feeding device is used to transport contaminated soil and perform preliminary crushing. A grading and screening device, comprising at least three stages of screening equipment, is used to separate pre-crushed soil into at least three grades: coarse, medium, and fine particles according to particle size. The multi-stage rinsing device is equipped with at least three rinsing units that match the sieving level of the grading and screening device. The rinsing units are used to perform targeted rinsing on soils of different particle sizes. A compound rinsing agent adjustment device includes multiple rinsing agent storage units, a detection unit, and an adjustment unit. The detection unit is used to monitor the concentration of contaminants and pH value in the rinsing solution in real time. The adjustment unit adjusts the type, concentration, and pH value of the rinsing agent according to the monitoring results of the detection unit and delivers it to the multi-stage rinsing device. The rinsing solution circulation and replenishment device includes a flocculation and sedimentation unit, an oxidation and regeneration unit, and a concentration adjustment unit connected in sequence. The flocculation and sedimentation unit is used to remove heavy metal precipitates from the rinsing solution, the oxidation and regeneration unit is used to degrade organic matter in the rinsing solution, and the concentration adjustment unit is used to adjust the concentration of the regenerated rinsing solution for circulation to the multi-stage rinsing device.

2. The system according to claim 1, characterized in that, The three-stage screening equipment of the grading and screening device includes a drum screen, a hydrocyclone and a vibrating screen; wherein, the drum screen is used to screen out coarse soil particles with a particle size greater than 2mm, the combined dewatering device screens medium soil particles with a particle size of 0.15-2mm, and the vibrating screen is used to screen fine soil particles with a particle size less than 0.15mm.

3. The system according to claim 1, characterized in that, In the three-stage rinsing unit of the multi-stage rinsing device: For coarse-grained soil, the rinsing unit uses clean water rinsing, controls the pH value to 2.0-3.0, the liquid-solid ratio to 1:4-1:6, and the treatment time to 1-3 hours; For the leaching unit targeting medium-particle soil, a compound leaching agent consisting of chelating agents and surfactants is used, with the pH value controlled at 5.5-6.5, the liquid-solid ratio at 1:2-1:4, and the treatment time at 3-5 hours. For the leaching unit of fine-particle soil, a compound leaching agent of strong chelating agent and oxidant is used, the pH value is controlled at 2.5-3.5, the liquid-solid ratio is 1:1-1:3, and the treatment time is 1-1.5 hours.

4. The apparatus according to claim 1, characterized in that, The rinsing agent storage unit of the compound rinsing agent conditioning device includes a chelating agent, a surfactant, a reducing agent, and an oxidizing agent; wherein the chelating agent is selected from ethylenediaminetetraacetic acid or sodium N-dodecylethylenediaminetriacetate, the surfactant is selected from rhamnolipid or saponin, and the reducing agent is selected from ascorbic acid or sodium oxalate.

5. The system according to claim 1, characterized in that, The regulating unit of the compound leaching agent regulating device adopts a "reduction before leaching" strategy for compound contaminated soil: first, the organic matter in the soil is decomposed by the reducing agent, and then the heavy metals and residual organic matter are simultaneously leached by the compound solution of chelating agent and surfactant.

6. The system according to claim 1, characterized in that, The flocculation and sedimentation unit of the rinsing fluid recycling device adds polyaluminum chloride and polyacrylamide for coagulation and sedimentation, and controls the pH value to 7-8.

7. The apparatus according to claim 1, characterized in that, The oxidative regeneration unit of the rinsing solution circulation and replenishment device adopts ozone / persulfate synergistic oxidation technology, controlling the ozone dosage to 0.7-0.8 kg / kg chemical oxygen demand (not an effluent indicator that needs to be discharged into the external water body, but a design parameter characterizing the pollutant load in the reaction unit), the sodium persulfate concentration to 4000-5000 mg / L, the pH value to 8.5-9.5, and the reaction time to 180-240 minutes.

8. The system according to claim 1, characterized in that, The concentration adjustment unit of the rinsing fluid circulation and regeneration device is a rinsing fluid generator. The rinsing fluid generator controls the concentration of the rinsing fluid by means of current and mother liquor flow rate. The mother liquor includes potassium hydroxide solution, sodium hydroxide solution or ethylenediaminetetraacetic acid solution.

9. The system according to claim 1, characterized in that, The grading and screening device and the multi-stage leaching device form a closed-loop linkage through the control system. The screened soil automatically enters the corresponding level of leaching unit, and the leaching liquid circulates between the multi-stage leaching device and the leaching liquid recycling and regeneration device through pipelines.

10. The system according to claim 1, characterized in that, The control system is a distributed control system, which integrates a 5G cloud IoT module to realize real-time monitoring, automatic adjustment and remote management of equipment operating parameters.

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