River sediment heavy metal environment-friendly separation method and system based on multi-stage combined treatment

Abstract

The invention provides a river sediment heavy metal environment-friendly separation method and system based on multi-stage combined treatment. The method comprises the steps that a pretreatment module achieves sediment gradient layered screening through a vibration screening device, and ferromagnetic heavy metal is separated in combination with a magnetic separation composite device; the main body treatment module adopts an electrodynamics-micro-nano bubble coupling reaction tank, a colloid structure is broken through a micro-nano bubble cavitation effect, migration of non-ferromagnetic heavy metal ions is accelerated in combination with a directional electric field, and a coordination agent is added to enhance a separation effect; the deep treatment module realizes deep capture of heavy metal ions and heavy metal compounds through a double-layer adsorption medium of a modified biochar composite material and sulfydryl modified diatomite. According to the system, through physical screening, magnetic separation, electrochemistry and adsorption technologies, heavy metals in different forms are precisely separated step by step, and the overall treatment efficiency and the heavy metal removal rate are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection treatment technology, and specifically to a method and system for environmentally friendly separation of heavy metals in river sediment based on multi-stage combined treatment. Background Art

[0002] Current river sediment heavy metal treatment systems generally have problems with static solidification of process parameters and delayed dynamic response. Traditional methods rely on manually preset fixed treatment processes, which are difficult to adapt to the dynamic changes in the occurrence forms of heavy metals. When the sediment environment causes heavy metal form transformation due to changes in hydrological conditions, existing technologies are unable to achieve automatic optimization of graded treatment strategies, resulting in failure of coordination between multi-stage treatment units, and a significant decrease in physical sorting accuracy and chemical treatment efficiency. At the same time, mainstream processes focus too much on pollutant separation and ignore resource closed-loop design. The treated heavy metal waste lacks the ability to be directional enriched, resulting in secondary pollution risks and waste of resources.

[0003] The existing technology system has two shortcomings in data governance and system integration: on the one hand, multi-source heterogeneous detection data leads to inaccurate matching between pollution traceability and process parameters due to differences in temporal and spatial resolution and the lack of feature analysis models; on the other hand, the processing equipment lacks intelligent expansion capabilities, parameter control relies on manual experience and the cost of system expansion is high, especially the insufficient ability to identify and recover associated metals, resulting in long-term high comprehensive processing costs, seriously restricting the promotion of engineering applications. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the current background technology, the purpose of the present invention is to provide a method and system for environmentally friendly separation of heavy metals in river sediment based on multi-stage combined treatment.

[0005] To this end, the present invention adopts the following technical solutions:

[0006] The environmentally friendly river sediment heavy metal separation system based on multi-stage combined treatment includes:

[0007] A pretreatment module, comprising a vibration screening device and a magnetic separation composite device, wherein the vibration screening device stratifies the heavy metal-contaminated sludge, and the magnetic separation composite device separates the ferromagnetic heavy metals in the sludge to obtain the first-state sludge;

[0008] The main processing module is configured to separate the non-ferromagnetic heavy metals in the first-state sediment by transferring the first-state sediment to a preset reaction tank to generate the second-state sediment;

[0009] The deep treatment module is provided with an adsorption tower containing a double-layer adsorption medium, which uses the double-layer adsorption medium to adsorb the heavy metals remaining in the second-state sediment to generate a third-state sediment;

[0010] The third-state sludge is subjected to a final inspection. If it does not meet the standards, it is returned to the main processing module for reprocessing.

[0011] Furthermore, the vibrating screening device adopts a three-layer stacked screen structure, and is equipped with an electromagnetic exciter at the bottom to drive the screen to produce vertical and horizontal vibrations. The three layers of stacked screens are connected by rigid connecting rods and spring groups; the apertures of the three layers of stacked screens decrease from top to bottom, and the first particle layer, the second particle layer and the third particle layer are screened out respectively.

[0012] Furthermore, the first particle layer directly enters a preset flushing channel and is deemed to meet the standards after being flushed;

[0013] The second particle layer is transferred to the magnetic separation composite device,

[0014] The magnetic separation composite device is provided with a crushing chamber and a permanent magnetic roller;

[0015] The second particle layer enters the crushing chamber and is struck by the rotating tungsten steel hammer head installed in the crushing chamber. When the heavy metals in the second particle layer are exposed, they are transferred to the permanent magnetic roller.

[0016] Several permanent magnets are arranged in a sector-shaped partition along the axial direction at a preset angle inside the permanent magnet drum. The permanent magnets are arranged alternately with N and N poles, so that a radial magnetic field is formed on the surface of the permanent magnet drum. The magnetic field intensity decreases from the center of the drum along the radius of the drum to the surface of the drum.

[0017] The ferromagnetic heavy metals exposed in the second particle layer are attracted to the surface of the permanent magnet roller by the permanent magnet, and then fall into the preset shaking guide trough;

[0018] The magnetic field force on the surface of the permanent magnet drum The calculation formula is as follows:

[0019]

[0020] in, is the magnetic susceptibility of the ferromagnetic heavy metal particles, V is the volume of the ferromagnetic heavy metal particles, is the magnetic permeability, B is the magnetic field intensity on the surface of the permanent magnet roller, is the rate of change of magnetic field intensity with space;

[0021] The rate of change of magnetic field strength with space The calculation formula is as follows:

[0022]

[0023] in, is the magnetic field strength on the surface of the permanent magnet, is the permanent magnet spacing, is the angle of the sector partition;

[0024] The magnetic separation composite device adjusts the magnetic field intensity B on the surface of the permanent magnet roller and the distance between the permanent magnets. and sector partition angle ,control To separate different ferromagnetic heavy metal particles;

[0025] The third particle layer directly enters the permanent magnet drum for separation of ferromagnetic heavy metal particles.

[0026] Furthermore, before the first-state sludge is transported to the main processing module, the moisture content needs to be adjusted;

[0027] The steps for adjusting moisture content are as follows:

[0028] The magnetic separation composite device also has built-in spiral extrusion dehydration components and atomization spray components;

[0029] The microwave humidity sensor built into the magnetic separation composite device detects in real time whether its moisture content deviates from the preset target range.

[0030] If the moisture content is higher than the maximum value of the target range, the first-state sludge enters the spiral extrusion dehydration component; the spiral extrusion dehydration component removes moisture from the first-state sludge by uniformly increasing the internal pressure until the moisture content of the first-state sludge is within the target range;

[0031] If the moisture content is lower than the minimum value of the target range, the first-state sludge passes through the atomizing spray component; the atomizing spray component evenly sprays deionized water or water used to flush the first particle layer on the first-state sludge, and stirs and mixes it through the built-in paddle until the moisture content of the first-state sludge is within the target range.

[0032] Furthermore, a micro-nano bubble generator is provided in the reaction tank for releasing micro-nano bubble groups;

[0033] The micro-nano bubble generation process is as follows: the micro-nano bubble generator is connected to an oxidant storage tank, the oxidant storage tank introduces a gaseous oxidant into the micro-nano bubble generator, and simultaneously introduces hydrogen peroxide into the micro-nano bubble generator to obtain a first gas-liquid mixture;

[0034] The micro-nano bubble generator is internally provided with a booster pump device, a microporous ceramic membrane device and a microporous structure device;

[0035] The booster pump device pressurizes the first gas-liquid mixture so that the gaseous oxidant is fully dissolved in the hydrogen peroxide to obtain a second gas-liquid mixture;

[0036] The second gas-liquid mixture is decompressed when passing through the microporous ceramic membrane device, causing the gaseous oxidant to change from a dissolved state to a saturated state and rapidly precipitate to form tiny bubble nuclei;

[0037] The second gas-liquid mixture carries tiny bubble nuclei and flows through the microporous structure device. The tiny bubble nuclei are broken into micro-nano bubbles by turbulent shear force. At the same time, the pressure difference between the inlet and outlet of the second gas-liquid mixture when it flows through the microporous structure device is monitored by a pressure sensor. ;

[0038] After the micro-nano bubble group contacts the first-state bottom mud, it decomposes the double-layer structure of the colloid in the first-state bottom mud through the cavitation effect, releases the non-ferromagnetic heavy metal ions wrapped by the colloid, and enhances the activity of the non-ferromagnetic heavy metal ions.

[0039] The micro-nano bubble size The control formula is as follows:

[0040]

[0041] Where, σ is the interfacial tension between hydrogen peroxide and gaseous oxidant, ρ is the density of the first-state sediment, is the flow rate of the gaseous oxidant, u is the flow resistance of the bottom mud in the first state, is the hydrogen peroxide flow rate;

[0042] In the micro-nano bubble generator, the flow rate of the gaseous oxidant is adjusted. and pressure difference Controlling the size of micro-nano bubbles , to enhance the cavitation effect.

[0043] Furthermore, after the first-state sludge is treated by the micro-nano bubble generator, the electrode group and the complexing agent dosing pump provided in the reaction tank are used to separate the non-ferromagnetic heavy metal ions in the first-state sludge to obtain the second-state sludge;

[0044] The working process of the electrode group is as follows: the electrode group applies a DC pulse electric field to form a directional electric field. In the directional electric field, anode materials and cathode materials are arranged in a staggered array to form anode and cathode regions. Positively charged non-ferromagnetic heavy metal ions migrate toward the cathode region, while negatively charged non-ferromagnetic heavy metal ions migrate toward the anode region, thereby separating the non-ferromagnetic heavy metal ions.

[0045] The calculation formula for the migration rate of the non-ferromagnetic heavy metal ions in the directional electric field is as follows:

[0046]

[0047] in, is the movement speed of the i-th non-ferromagnetic heavy metal ion, is the average migration velocity of the i-th non-ferromagnetic heavy metal ion under unit electric field strength, is the directional electric field intensity, is the spontaneous diffusion rate of the i-th non-ferromagnetic heavy metal ion due to its own concentration gradient, is the concentration of the i-th non-ferromagnetic heavy metal ion, is the position variable of the non-ferromagnetic heavy metal ion along the direction of the electric field;

[0048] Accelerating the directional migration of the non-ferromagnetic heavy metal ions by adjusting the directional electric field strength E in the reaction cell;

[0049] The ligand dosing pump is located on the side wall of the reaction tank. The ligand forms a complex with the non-ferromagnetic heavy metal ions. The complex carries negative charge and migrates to the anode area to separate the non-ferromagnetic heavy metal ions.

[0050] The second-state sludge is transferred to the adsorption tower.

[0051] Furthermore, the double-layer adsorption medium in the adsorption tower is in full contact with the second-state bottom mud;

[0052] The double-layer adsorption medium includes a biochar composite material and thiol-modified diatomaceous earth. The pore structure of the biochar composite material captures the heavy metal ions remaining in the second-state sediment. At the same time, the thiol-modified diatomaceous earth fixes the heavy metal compounds remaining in the second-state sediment through chemical bonds.

[0053] During the adsorption process, multiple monitoring probes are installed inside the adsorption tower to monitor the adsorption saturation of the double-layer adsorption medium in real time;

[0054] When the adsorption saturation reaches a preset threshold, the double-layer adsorption medium is cleaned by an air-water combined backwashing device provided in the adsorption tower.

[0055] Furthermore, the third-state sludge is tested for heavy metal content; the third-state sludge that meets the standards is dehydrated and formed and then transferred to safe landfill or resource utilization, while the third-state sludge that does not meet the standards is returned to the reaction tank for further treatment.

[0056] An environmentally friendly method for separating heavy metals from river sediment based on multi-stage combined treatment, the method comprising:

[0057] Step 1: Separate the heavy metal-contaminated sediment by a vibration screening device; and separate the ferromagnetic heavy metals in the sediment by a magnetic separation composite device to obtain the first-state sediment;

[0058] Step 2: transferring the first-state sludge to a reaction tank to separate the non-ferromagnetic heavy metals in the first-state sludge to generate the second-state sludge;

[0059] Step 3: transferring the second-state sludge to an adsorption tower containing a double-layer adsorption medium, and using the double-layer adsorption medium to adsorb the heavy metals remaining in the second-state sludge to generate a third-state sludge;

[0060] Step 4: Perform a final inspection on the third-state sludge. If it does not meet the standards, it will be returned to the reaction tank for further treatment.

[0061] 1. The present invention adopts a three-level modular design of pretreatment, main treatment and deep treatment, combined with vibration screening, magnetic field separation, electrochemistry and adsorption technology, to dynamically adapt to the changes in heavy metal morphology, effectively solve the problem of synergistic failure caused by the solidification of traditional process parameters, and improve separation accuracy and treatment efficiency;

[0062] 2. The present invention achieves directional enrichment and resource utilization of heavy metals by introducing magnetic heavy metal recovery, adsorption medium regeneration and sediment return mechanisms, significantly reduces the risk of secondary pollution, and forms a closed-loop system of pollution control and resource recovery;

[0063] 3. The present invention supports dynamic adjustment of key parameters through integrated sensor monitoring and real-time feedback mechanism, reduces manual dependence, and enhances the system's adaptive processing capability for complex sediment environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0065] Figure 1 Schematic diagram of the system workflow of the present invention;

[0066] Figure 2 This is a schematic diagram of the pre-processing module flow of the present invention;

[0067] Figure 3 Schematic diagram of the micro-nano bubble generation process of the present invention. DETAILED DESCRIPTION

[0068] To achieve the above objectives, the present invention is implemented through the following technical solutions: the present invention provides a riverbed sediment heavy metal environmental separation system based on multi-stage combined treatment, please refer to Figures 1 to 3 , the system comprises:

[0069] In the pretreatment module, the sediment contaminated by heavy metals enters the vibration screening device, which screens the sediment in layers through multi-stage vibration, so that the heavy metals are concentrated in different diameter ranges, forming the basis for layered treatment.

[0070] In this embodiment, the vibrating screening device adopts a three-layer stacked screen structure. The screen surface is made of polyurethane material. The three layers of stacked screen are connected by rigid connecting rods and spring groups to achieve multi-level vibration. The apertures of the three layers of stacked screen are set to 2mm, 0.5mm and 0.1mm in the upper, middle and lower layers respectively, forming a gradient stratification system:

[0071] The first granular layer (>2mm): mainly composed of sand, gravel, and organic debris, with low heavy metal content;

[0072] Second granular layer (0.5-2 mm): contains clay aggregates that partially adsorb heavy metals;

[0073] The third granular layer (<0.5mm): enriched with more than 70% of heavy metal particles.

[0074] The bottom of the vibrating screening device is equipped with an electromagnetic exciter to drive the screen body to produce vertical and horizontal composite vibrations. The vibration (20-50Hz) causes the bottom mud to jump on the screen surface to achieve layered screening.

[0075] The vibrating screening device is equipped with bouncing balls to prevent sticky sediment from clogging the screen holes, and is also equipped with a spray system to clean the screen surface.

[0076] The vibration of the screen body drives the bouncing ball to bounce randomly and continuously hit the back of the upper screen (the impact frequency is synchronized with the vibration). The diameter of the bouncing ball needs to be slightly larger than the diameter of the screen hole to avoid it getting stuck in the screen hole;

[0077] The spray system automatically starts spraying and cleaning the screen surface according to a preset cycle (such as every 10 minutes).

[0078] The first granular layer directly enters the preset channel and reaches the standard after flushing;

[0079] The second particle layer is transported to the magnetic separation compound device;

[0080] The magnetic separation composite device is provided with a crushing chamber and a permanent magnetic roller;

[0081] In this embodiment, the second particle layer enters the crushing chamber, where a tungsten steel hammer is installed to strike the clay mass wrapped with heavy metals at a rotation speed of 1500-3000 r / min. The impact energy reaches 20-50 J / cm², exposing the wrapped heavy metals. The heavy metals in the second particle layer are exposed and then transferred to the permanent magnet roller.

[0082] In this embodiment, NdFeB permanent magnets are arranged in 60° sectors along the axial direction of the permanent magnet drum, with N and N poles alternately arranged, so that a radial magnetic field is formed on the surface of the permanent magnet drum. The magnetic field intensity decreases from the center of the drum along the drum radius to the drum surface.

[0083] The NdFeB permanent magnet attracts the ferromagnetic heavy metals exposed in the second particle layer to the surface of the permanent magnet drum, and the metals fall into the preset shaking guide trough to obtain the first state bottom mud;

[0084] Magnetic field force on the surface of permanent magnet drum The calculation formula is as follows:

[0085]

[0086] in, is the magnetic susceptibility of the ferromagnetic heavy metal particles, V is the volume of the ferromagnetic heavy metal particles, is the magnetic permeability, B is the magnetic field intensity on the surface of the permanent magnet roller, is the rate of change of magnetic field intensity with space;

[0087] The rate of change of magnetic field strength with space The calculation formula is as follows:

[0088]

[0089] in, is the magnetic field strength on the surface of the permanent magnet, is the permanent magnet spacing, is the angle of the magnetic pole sector.

[0090] The magnetic separation composite device adjusts the magnetic field intensity B on the surface of the permanent magnet roller, the permanent magnet spacing d and the sector partition angle. ,control To separate different ferromagnetic heavy metal particles (such as Fe, Ni).

[0091] The third particle layer directly enters the permanent magnet drum for separation of ferromagnetic heavy metal particles;

[0092] The moisture content of the first-state sludge is adjusted and transported to the main processing module.

[0093] In this embodiment, the moisture content is adjusted by using a microwave humidity sensor built into the magnetic separation composite device to detect in real time whether the current moisture content deviates from a preset target range of 25% to 45%.

[0094] The magnetic separation composite device also has built-in spiral extrusion dehydration components and atomization spray components;

[0095] If the moisture content is too high (e.g. >45%), the first-state sludge enters the preset spiral extrusion dehydration component, where moisture is removed through a progressive pressure gradient to prevent heavy metals from being lost with the water flow until the moisture content of the first-state sludge is within the target range.

[0096] If the moisture content is too low (e.g. <25%), the atomizing spray component evenly sprays deionized water or water recycled from treating the coarse particle layer sludge, and at the same time sets a paddle mixer to mix at a low speed to prevent local over-wetting and agglomeration, until the moisture content of the sludge in the first state is within the target range.

[0097] The main processing module evenly injects the first-state sludge into the reaction tank. At this time, the first-state sludge adjusted to an appropriate moisture content is in an optimal solid-liquid mixing state, which not only retains sufficient moisture to maintain electric field conduction, but also avoids excessive moisture dilution of the reaction system. The reaction system refers to the multiphase reaction environment inside the reaction tank.

[0098] A micro-nano bubble generator is provided in the reaction pool, and the micro-nano bubble generator releases micro-nano bubbles to form a high-density micro-nano bubble group. The micro-nano bubble generator is connected to an oxidant storage tank, and the oxidant storage tank introduces a gaseous oxidant into the micro-nano bubble generator. At the same time, hydrogen peroxide is introduced into the micro-nano bubble generator from the outside to obtain a first gas-liquid mixture;

[0099] In this embodiment, the micro-nano bubble generation process is as follows:

[0100] The micro-nano bubble generator is equipped with a booster pump device, a microporous ceramic membrane device and a microporous structure device;

[0101] The first gas-liquid mixture is pressurized to 0.5-3 MPa by the booster pump device, so that the gas is fully dissolved in the liquid to obtain a second gas-liquid mixture;

[0102] When the second gas-liquid mixture passes through the microporous ceramic membrane device, the pressure is reduced, and the gaseous oxidant changes from a dissolved state to a saturated state and is rapidly precipitated to form tiny bubble nuclei;

[0103] The second gas-liquid mixture carries tiny bubble nuclei and flows through a microporous structure device (pore size 1-50μm). The bubble nuclei are broken into micro-nano bubbles of 50-200nm by turbulent shear force. At the same time, the pressure difference between the inlet and outlet of the second gas-liquid mixture when it flows through the microporous structure device is monitored by a pressure sensor. ;

[0104] The micro-nano bubble group is in full contact with the colloid in the first-state bottom mud. The surface of the micro-nano bubble group effectively decomposes the double-layer structure of the colloid in the first-state bottom mud through the cavitation effect, releases the non-ferromagnetic heavy metal ions wrapped by the colloid, and enhances the activity of the non-ferromagnetic heavy metal ions.

[0105] The micro-nano bubble size control formula is as follows:

[0106]

[0107] Where, σ is the interfacial tension between hydrogen peroxide and gaseous oxidant, ρ is the density of the first-state sediment, is the flow rate of the gaseous oxidant, u is the flow resistance of the bottom mud in the first state, is the hydrogen peroxide flow rate;

[0108] In the micro-nano bubble generator, by adjusting the gas flow and pressure difference ,control To enhance the cavitation effect of micro-nano bubbles and promote the breakdown of the colloidal structure. The intensity of the cavitation effect is inversely proportional to the cube of the micro-nano bubble size.

[0109] After the first-state sediment is treated by the micro-nano bubble generator, it is then combined with the electrode group and complexing agent dosing pump in the reaction tank to separate the non-ferromagnetic heavy metal ions in the first-state sediment, which include paramagnetic heavy metal ions and diamagnetic heavy metal ions, to obtain the second-state sediment;

[0110] In this embodiment, an electrode group is provided in the reaction tank, and a 3-5V / cm DC pulse electric field is applied to the electrode group to form a directional electric field. In the directional electric field, anode materials and cathode materials are arranged in a staggered array to form anode and cathode regions. The distance between each pair of anodes and cathodes is 50 cm. The first-state bottom mud is adjusted to an appropriate moisture content to form a stable heavy metal ion migration channel. The positively charged non-ferromagnetic heavy metal ions migrate directionally toward the cathode region, and the negatively charged non-ferromagnetic heavy metal ions migrate directionally toward the anode region, thereby obtaining the second-state bottom mud.

[0111] The calculation formula for the migration rate of heavy metal ions in a directional electric field is as follows:

[0112]

[0113] in, is the movement speed of the i-th non-ferromagnetic heavy metal ion, is the average migration velocity of the i-th non-ferromagnetic heavy metal ion under unit electric field strength, is the directional electric field intensity, is the spontaneous diffusion rate of the i-th non-ferromagnetic heavy metal ion due to its own concentration gradient, is the concentration of the i-th non-ferromagnetic heavy metal ion, is the position variable of the non-ferromagnetic heavy metal ion along the direction of the electric field;

[0114] In the reaction cell, the directional migration of non-ferromagnetic heavy metal ions is accelerated by adjusting the directional electric field strength E.

[0115] Since the first-stage sediment usually contains a variety of non-ferromagnetic heavy metal ions such as Pb, Cd, and Cr, and their migration rates are different (for example, the migration rate of Cd²⁺ is 1.3 times faster than that of Pb²⁺), resulting in incomplete separation of non-ferromagnetic heavy metal ions, a specific ligand is injected through the ligand dosing pump on the side wall of the reaction tank. The ligand forms a stable complex with the non-ferromagnetic heavy metal ions, and the complex carries a negative charge and migrates toward the anode area.

[0116] Complexing agent dosage The calculation formula is as follows:

[0117]

[0118] in, is the preset safety factor, For the Heavy metal concentrations, is the volume of the first state processed, is the coordination number.

[0119] The deep processing module transports the second-state sludge to the adsorption tower;

[0120] The adsorption tower is filled with a double-layer adsorption medium consisting of a biochar composite material and thiol-modified diatomaceous earth. The double-layer adsorption medium is in full contact with the second-state sediment. The pore structure of the biochar composite captures the heavy metal ions remaining in the second-state sediment, while the thiol-modified diatomaceous earth fixes the heavy metal compounds through chemical bonds, resulting in the third-state sediment.

[0121] During the treatment process, multiple monitoring probes are installed inside the adsorption tower to monitor the adsorption saturation of the double-layer adsorption medium in real time;

[0122] When the adsorption saturation reaches the preset threshold, the air-water combined backwash device installed in the adsorption tower automatically starts;

[0123] The air-water combined backwash device generates high-pressure gas and water flow. Under the action of high-pressure gas and water flow, the double-layer adsorption medium will be fluidized, stripping off the heavy metal ions and heavy metal compounds attached to the surface of the double-layer adsorption medium.

[0124] The effects of double-layer adsorption medium fluidization are as follows:

[0125] After long-term use of the double-layer adsorption medium, heavy metals and impurities tend to accumulate on the surface to form hard lumps. The double-layer adsorption medium fluidization process uses the air-water impact force to break up the lumps, restore the double-layer adsorption medium to a loose state, and maintain adsorption activity;

[0126] Fluidization allows the double-layer adsorption medium particles to fully collide and rub with the water flow, destroying the binding force between the heavy metals and the double-layer adsorption medium, and stripping the pollutants from the surface of the double-layer adsorption medium;

[0127] Fluidization allows the double-layer adsorption medium particles to tumble and flow in the reaction tower, avoiding local blockage or uneven cleaning problems that occur during the regeneration of traditional double-layer adsorption media, ensuring that each double-layer adsorption medium particle can be thoroughly cleaned;

[0128] The fluidized double-layer adsorption medium can prolong the service life and can be reused dozens of times, reducing the replacement frequency and lowering the processing cost;

[0129] The fluidization process can promptly eliminate the risk of blockage in the adsorption tower, maintain smooth water flow in the adsorption tower, avoid shutdown and maintenance caused by the hardening of the double-layer adsorption medium, and improve the overall processing efficiency.

[0130] Minimum backwash flow rate required for fluidization of double-layer adsorption media The calculation formula is as follows:

[0131]

[0132] in, is the diameter of the double-layer adsorption medium particles, is the density of the double-layer adsorption medium, is the density of the mixture of gas and water, is the drag coefficient, which is related to the particle shape and fluid viscosity, is the acceleration due to gravity.

[0133] Verify the heavy metal content of the third-state sediment.

[0134] In this embodiment, a multi-point automatic sampler is set up to randomly collect third-state sediment samples at preset time or mass intervals (such as every batch or every 10 tons) to avoid human interference;

[0135] After the collected samples were crushed and homogenized, they were subjected to acid hydrolysis (using HNO3-HF mixed acid) in a microwave digester (temperature 180-220°C) to convert the solid heavy metals into detectable ions;

[0136] Using X-ray fluorescence spectrometer (XRF) for non-destructive testing, semi-quantitative data (accuracy ±10%) for heavy metals such as Cd, Pb, and As can be obtained within 30 seconds for preliminary compliance assessment.

[0137] For samples exceeding the standard (XRF data close to the preset threshold), inductively coupled plasma mass spectrometry (ICP-MS) is used for trace analysis, with a detection limit as low as 0.01 ppm, to ensure compliance with the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard" (GB 15618-2018);

[0138] The third-state sludge that meets the standards is dehydrated and formed before being transferred to safe landfill or resource utilization, while the third-state sludge that does not meet the standards is returned to the main treatment module for further treatment.

[0139] An environmentally friendly method for separating heavy metals from river sediment based on multi-stage combined treatment, the method comprising:

[0140] Step 1: Separate the heavy metal-contaminated sediment by a vibration screening device; and separate the ferromagnetic heavy metals in the sediment by a magnetic separation composite device to obtain the first-state sediment;

[0141] Step 2: transferring the first-state sludge to a reaction tank to separate the non-ferromagnetic heavy metals in the first-state sludge to generate the second-state sludge;

[0142] Step 3: transferring the second-state sludge to an adsorption tower containing a double-layer adsorption medium, and using the double-layer adsorption medium to adsorb the heavy metals remaining in the second-state sludge to generate a third-state sludge;

[0143] Step 4: Perform a final inspection on the third-state sludge. If it does not meet the standards, it will be returned to the reaction tank for further treatment.

[0144] In summary, the present invention adopts a three-stage modular design of pretreatment, main treatment and deep treatment, combined with physical screening, magnetic separation, electrochemistry and adsorption technology, to accurately separate heavy metals in different forms step by step, significantly improving the overall treatment efficiency and heavy metal removal rate.

[0145] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The environmentally friendly river sediment heavy metal separation system based on multi-stage combined treatment is characterized by: include: A pretreatment module, comprising a vibration screening device and a magnetic separation composite device, wherein the vibration screening device stratifies the heavy metal-contaminated sludge, and the magnetic separation composite device separates the ferromagnetic heavy metals in the sludge to obtain the first-state sludge; The main processing module is configured to separate the non-ferromagnetic heavy metals in the first-state sediment by transferring the first-state sediment to a preset reaction tank to generate the second-state sediment; The deep treatment module is provided with an adsorption tower containing a double-layer adsorption medium, which uses the double-layer adsorption medium to adsorb the heavy metals remaining in the second-state sediment to generate a third-state sediment; The third-state sludge is subjected to a final inspection. If it does not meet the standards, it is returned to the main processing module for reprocessing.

2. The system according to claim 1, wherein: The vibrating screening device adopts a three-layer stacked screen structure, and is equipped with an electromagnetic exciter at the bottom to drive the screen to produce vertical and horizontal vibrations. The three layers of stacked screens are connected by rigid connecting rods and spring groups; the apertures of the three layers of stacked screens decrease from top to bottom, and the first particle layer, the second particle layer and the third particle layer are screened out respectively.

3. The system according to claim 2, characterized in that The first granular layer directly enters the preset flushing channel and is deemed to meet the standards after being flushed; The second particle layer is transferred to the magnetic separation composite device, The magnetic separation composite device is provided with a crushing chamber and a permanent magnetic roller; The second particle layer enters the crushing chamber and is struck by the rotating tungsten steel hammer head installed in the crushing chamber. When the heavy metals in the second particle layer are exposed, they are transferred to the permanent magnetic roller. Several permanent magnets are arranged in a sector-shaped partition along the axial direction at a preset angle inside the permanent magnet drum. The permanent magnets are arranged alternately with N and N poles, so that a radial magnetic field is formed on the surface of the permanent magnet drum. The magnetic field intensity decreases from the center of the drum along the radius of the drum to the surface of the drum. The ferromagnetic heavy metals exposed in the second particle layer are attracted to the surface of the permanent magnet roller by the permanent magnet, and then fall into the preset shaking guide trough; The magnetic field force on the surface of the permanent magnet drum The calculation formula is as follows: in, is the magnetic susceptibility of the ferromagnetic heavy metal particles, V is the volume of the ferromagnetic heavy metal particles, is the magnetic permeability, B is the magnetic field intensity on the surface of the permanent magnet roller, is the rate of change of magnetic field intensity with space; The rate of change of magnetic field strength with space The calculation formula is as follows: in, is the magnetic field strength on the surface of the permanent magnet, is the permanent magnet spacing, is the angle of the sector partition; The magnetic separation composite device adjusts the magnetic field intensity B on the surface of the permanent magnet roller and the distance between the permanent magnets. and sector partition angle ,control To separate different ferromagnetic heavy metal particles; The third particle layer directly enters the permanent magnet drum for separation of ferromagnetic heavy metal particles.

4. The system according to claim 3, characterized in that Before the first-state sludge is transported to the main treatment module, the moisture content needs to be adjusted; The steps for adjusting moisture content are as follows: The magnetic separation composite device also has built-in spiral extrusion dehydration components and atomization spray components; The microwave humidity sensor built into the magnetic separation composite device detects in real time whether its moisture content deviates from the preset target range. If the moisture content is higher than the maximum value of the target range, the first-state sludge enters the spiral extrusion dehydration component; the spiral extrusion dehydration component removes moisture from the first-state sludge by uniformly increasing the internal pressure until the moisture content of the first-state sludge is within the target range; If the moisture content is lower than the minimum value of the target range, the first-state sludge passes through the atomizing spray component; the atomizing spray component evenly sprays deionized water or water used to flush the first particle layer on the first-state sludge, and mixes it through the built-in paddle mixer until the moisture content of the first-state sludge is in the target range.

5. The system according to claim 4, characterized in that The reaction tank is provided with a micro-nano bubble generator for releasing micro-nano bubble groups; The micro-nano bubble generation process is as follows: the micro-nano bubble generator is connected to an oxidant storage tank, the oxidant storage tank introduces a gaseous oxidant into the micro-nano bubble generator, and simultaneously introduces hydrogen peroxide into the micro-nano bubble generator to obtain a first gas-liquid mixture; The micro-nano bubble generator is internally provided with a booster pump device, a microporous ceramic membrane device and a microporous structure device; The booster pump device pressurizes the first gas-liquid mixture so that the gaseous oxidant is fully dissolved in the hydrogen peroxide to obtain a second gas-liquid mixture; The second gas-liquid mixture is decompressed when passing through the microporous ceramic membrane device, causing the gaseous oxidant to change from a dissolved state to a saturated state and rapidly precipitate to form tiny bubble nuclei; The second gas-liquid mixture carries tiny bubble nuclei and flows through the microporous structure device. The tiny bubble nuclei are broken into micro-nano bubbles by turbulent shear force. At the same time, the pressure difference between the inlet and outlet of the second gas-liquid mixture when it flows through the microporous structure device is monitored by a pressure sensor. ; After the micro-nano bubble group contacts the first-state bottom mud, it decomposes the double-layer structure of the colloid in the first-state bottom mud through the cavitation effect, releases the non-ferromagnetic heavy metal ions wrapped by the colloid, and enhances the activity of the non-ferromagnetic heavy metal ions. The micro-nano bubble size The control formula is as follows: Where, σ is the interfacial tension between hydrogen peroxide and gaseous oxidant, ρ is the density of the first-state sediment, is the flow rate of the gaseous oxidant, u is the flow resistance of the bottom mud in the first state, is the hydrogen peroxide flow rate; In the micro-nano bubble generator, the flow rate of the gaseous oxidant is adjusted. and pressure difference Controlling the size of micro-nano bubbles , to enhance the cavitation effect.

6. The system according to claim 5, characterized in that After the first-state sludge is treated by the micro-nano bubble generator, the electrode group and the complexing agent dosing pump provided in the reaction tank are used to separate the non-ferromagnetic heavy metal ions in the first-state sludge to obtain the second-state sludge; The working process of the electrode group is as follows: a DC pulse electric field is applied to the electrode group to form a directional electric field. In the directional electric field, anode materials and cathode materials are arranged in a staggered array to form anode and cathode regions. Positively charged non-ferromagnetic heavy metal ions migrate toward the cathode region, while negatively charged non-ferromagnetic heavy metal ions migrate toward the anode region. To separate non-ferromagnetic heavy metal ions; The calculation formula for the migration rate of the non-ferromagnetic heavy metal ions in the directional electric field is as follows: in, is the movement speed of the i-th non-ferromagnetic heavy metal ion, is the average migration velocity of the i-th non-ferromagnetic heavy metal ion under unit electric field strength, is the directional electric field intensity, is the spontaneous diffusion rate of the i-th non-ferromagnetic heavy metal ion due to its own concentration gradient, is the concentration of the i-th non-ferromagnetic heavy metal ion, is the position variable of the non-ferromagnetic heavy metal ion along the direction of the electric field; Accelerating the directional migration of the non-ferromagnetic heavy metal ions by adjusting the directional electric field strength E in the reaction cell; The ligand dosing pump is located on the side wall of the reaction tank. The ligand forms a complex with the non-ferromagnetic heavy metal ions. The complex carries negative charge and migrates to the anode area to separate the non-ferromagnetic heavy metal ions. The second-state sludge is transferred to the adsorption tower.

7. The system according to claim 6, characterized in that The double-layer adsorption medium in the adsorption tower is in full contact with the second-state bottom mud; The double-layer adsorption medium includes a biochar composite material and thiol-modified diatomaceous earth. The pore structure of the biochar composite material captures the heavy metal ions remaining in the second-state sediment. At the same time, the thiol-modified diatomaceous earth fixes the heavy metal compounds remaining in the second-state sediment through chemical bonds. During the adsorption process, multiple monitoring probes are installed inside the adsorption tower to monitor the adsorption saturation of the double-layer adsorption medium in real time; When the adsorption saturation reaches a preset threshold, the double-layer adsorption medium is cleaned by an air-water combined backwashing device provided in the adsorption tower.

8. The system according to claim 7, characterized in that The third-state sludge is tested for heavy metal content; the third-state sludge that meets the standards is dehydrated and formed and then transferred to safe landfill or resource utilization, while the third-state sludge that does not meet the standards is returned to the reaction tank for further treatment.

9. An environmentally friendly method for separating heavy metals from river sediment based on multi-stage combined treatment, characterized in that: include: Step 1: stratify the heavy metal contaminated sediment using a vibrating screening device; The ferromagnetic heavy metals in the sediment are separated by a magnetic separation composite device to obtain the first-state sediment; Step 2: transferring the first-state sludge to a reaction tank to separate the non-ferromagnetic heavy metals in the first-state sludge to generate the second-state sludge; Step 3: transferring the second-state sludge to an adsorption tower containing a double-layer adsorption medium, and using the double-layer adsorption medium to adsorb the heavy metals remaining in the second-state sludge to generate a third-state sludge; Step 4: Perform a final inspection on the third-state sludge. If it does not meet the standards, it will be returned to the reaction tank for further treatment.

Images