Heavy metal contaminated soil remediation method based on biochar loading technology

Abstract

The invention relates to the field of soil heavy metal pollution remediation, and discloses a heavy metal pollution soil remediation method based on a biochar loading technology, a biochar spiral chiral topological structure is constructed through femtosecond laser etching, a CdS quantum dot and graphene oxide composite layer is loaded, and the heavy metal selective adsorption and photocatalytic reduction ability is enhanced; a repairing agent is dynamically released in combination with a magnetic field response type microcapsule, multi-physics field parameters are optimized by utilizing a reinforcement learning algorithm, and accurate regulation and control of heavy metal migration-transformation-fixation are realized; an ultraviolet light triggered self-repairing mechanism is introduced to repair microcapsule damage, and pyrolysis oxidation and acid leaching processes are synchronously adopted to recover heavy metals and regenerate biochar. According to the invention, the defects of poor material selectivity, uncontrollable release and non-circulation in the prior art are overcome, and efficient targeted repair and resource recovery are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of soil heavy metal pollution remediation, and specifically to a method for remediating heavy metal contaminated soil based on biochar loading technology. Background Art

[0002] In the technology of remediating heavy metal contaminated soil, biochar is widely used as an adsorption carrier due to its high porosity and rich surface functional groups. However, there is a fundamental contradiction in the functional design of traditional biochar-based materials: on the one hand, its non-directional adsorption characteristics lead to insufficient selectivity for highly toxic heavy metal ions (such as Cr 6+ , As 5+ ), making it difficult to preferentially remove target pollutants in the complex pollution scenario; on the other hand, the immobilized remediation agents (such as zero-valent iron, sulfide) are prone to uncontrollable release in the soil environment, resulting in premature consumption of the material or passivation effect caused by too high local concentration.

[0003] Existing studies have tried to improve the remediation efficiency through surface modification (such as graphene oxide coating) or external field assistance (such as electric field driving). However, the modified biochar is still limited by the uneven spatial distribution of immobilization sites, and the static setting of external field parameters cannot adapt to the dynamic changes of the soil environment, resulting in significant fluctuations in the remediation efficiency. In addition, the regeneration technology of failed biochar mainly focuses on pyrolysis activation, but ignores the synchronous recovery of loaded heavy metals, resulting in coexistence of resource waste and environmental risks.

[0004] Therefore, the present invention proposes a method for remediating heavy metal contaminated soil based on biochar loading technology to solve the deficiencies of the existing technology. Summary of the Invention

[0005] The present invention solves the problems of poor material adsorption selectivity, uncontrollable release of remediation agents, disconnection between regeneration process and heavy metal recovery in traditional biochar-based remediation technologies, and significant fluctuations in remediation efficiency in complex pollution scenarios. Through dynamic regulation of loading technology, the synergistic mechanism of selective adsorption and morphological transformation, and a closed-loop regeneration process, efficient targeted removal and resource recovery of heavy metals are achieved.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for remediating heavy metal contaminated soil based on biochar loading technology, comprising the following steps:

[0007] S1. Prepare a modified biochar matrix: Pyrolyze and pickling treat biomass raw materials to obtain porous biochar, and construct loading sites on its surface;

[0008] S2. Construct a dynamic loading system based on the biochar matrix: Fix microcapsules containing remediation materials on the loading sites, and the release behavior of the microcapsules is regulated by an external physical field;

[0009] S3. Dynamic regulation of the repair process: Real-time monitoring of soil environmental parameters, adjusting the physical field parameters according to the monitoring data, and driving the release of the repair material and the migration and fixation of heavy metals;

[0010] S4. Regeneration and recycling: After the repair is completed, trigger the self-repair mechanism to restore the function of the load system, and recycle the heavy metals and biochar.

[0011] Preferably, in step S1:

[0012] The pyrolysis is carried out in an inert gas atmosphere, the temperature is 500 - 800 °C, and the constant temperature time is 1 - 4 h;

[0013] The pickling uses nitric acid or hydrochloric acid solution, the concentration is 0.05 - 0.5 mol / L, and the treatment time is 12 - 36 h.

[0014] Preferably, in step S1, a helical chiral topological structure is formed on the surface of the biochar by laser etching, the chiral index is (n,m) = (5,2) - (9,4), the groove depth is 50 - 500 nm, and the spacing is 20 - 100 nm.

[0015] Preferably, in step S2:

[0016] The microcapsule includes a core and a shell, the core is a mixture of FeS nanoparticles and a polymer, and the shell is a graphene oxide - humic acid composite film doped with magnetic nanoparticles;

[0017] The release threshold of the microcapsule satisfies the formula:

[0018]

[0019] where, M s is the saturation magnetization intensity of the magnetic nanoparticles, H is the external magnetic field intensity, μ 0 is the vacuum permeability, σ s is the yield stress of the shell, and d is the thickness of the shell.

[0020] Preferably, the microcapsule is fixed in the helical chiral grooves of the biochar by ultraviolet curing, the ultraviolet light wavelength is 300 - 400 nm, the intensity is 30 - 100 mW / cm 2 , and the curing time is 5 - 20 min.

[0021] Preferably, in step S3, the adjustment of the physical field parameters is realized by a reinforcement learning model, the model takes the real-time data of soil pH, redox potential and heavy metal concentration as input, and the magnetic field intensity and ultraviolet light intensity as output, where:

[0022] The reinforcement learning model is the Q-learning algorithm, and its action space is defined as the magnetic field strength range of 0 - 200 kA / m and the ultraviolet light intensity range of 0 - 100 mW / cm 2 ;

[0023] The reward function of the model is the weighted difference between the heavy metal removal amount and the material consumption amount.

[0024] Preferably, in the step S3, the heavy metal migration is realized by dielectrophoretic force driven by a high-frequency alternating electric field, and its migration equation satisfies:

[0025]

[0026] where C is the heavy metal concentration, D is the diffusion coefficient, ∈ m is the dielectric constant of the medium, r is the particle radius, η is the viscosity, f CM is the Clausius-Mossotti factor.

[0027] Preferably, in the step S4, the self-healing mechanism is a thiol-ene click chemical reaction triggered by ultraviolet light, and its reaction formula is:

[0028]

[0029] Preferably, in the step S4, the heavy metal recovery is realized by pyrolysis oxidation and acid leaching, where the pyrolysis temperature is 500 - 800 °C and the acid leaching solution is 0.5 - 2 mol / L hydrochloric acid.

[0030] The present invention provides a method for repairing heavy metal contaminated soil based on biochar loading technology. It has the following beneficial effects:

[0031] 1. The present invention constructs a helical chiral topological structure on the surface of biochar by femtosecond laser etching, combines the heterojunction composite modification of quantum dots (CdS) and graphene oxide (GO), and utilizes the synergistic effect of geometric confinement effect and photocatalytic reduction ability to break through the limitations of traditional biochar with low heavy metal adsorption capacity and poor selectivity, and realizes the directional capture and morphological transformation of highly toxic heavy metals (such as Cr 6 + 、As 5+ ), especially suitable for the differential removal requirements of multivalent heavy metals in composite contaminated soil.

[0032] 2. The present invention proposes a magnetic field encoding type microcapsule dynamic loading technology. Through the doping of magnetic nanoparticles and the regulation of the rupture threshold formula, combined with the ultraviolet light cross-linking fixation process, the repair material (FeS-PEI) is precisely positioned and released on demand in the biochar trenches, overcoming the defects of uneven material dispersion and low utilization rate in traditional static loading technologies. At the same time, through the synergy of dielectrophoretic migration and photocatalytic reaction, the spatial enrichment and chemical conversion efficiency of heavy metal ions are enhanced.

[0033] 3. The present invention constructs an intelligent regulation model based on the reinforcement learning algorithm. Taking the soil pH, redox potential, and heavy metal concentration gradient monitored in real time as input parameters, the physical field action parameters such as magnetic field intensity, electric field frequency, and ultraviolet light intensity are dynamically optimized to form a "perception - decision - execution" closed-loop control, solving the problems of parameter lag or excessive consumption in experience-driven repair technologies, and significantly improving the stability and self-adaptability of the repair process in complex pollution scenarios.

[0034] 4. The present invention introduces a thiol-ene click chemistry self-healing mechanism triggered by ultraviolet light. By online repairing the damage of the microcapsule shell, the service life of the dynamic loading system is extended; simultaneously, a combined process of pyrolysis oxidation - acid leaching is developed to convert the heavy metals in the failed biochar into recyclable forms (such as Cd 2+ ), realizing the circular regeneration and resource recovery of the repair material, and forming a full life cycle technical path of "pollution repair - material regeneration - resource recovery", significantly reducing the long-term cost of environmental governance.

[0035] 5. Through the multi-dimensional technology integration of quantum dot photocatalysis, dielectrophoretic migration, intelligent algorithm regulation, and self-healing chemistry, the present invention constructs a full-chain solution for the recognition, migration, transformation, fixation, and recovery of heavy metals on the biochar carrier, systematically solving the problems that traditional single technologies are difficult to take into account the complex occurrence forms of heavy metals, irreversible loss of repair materials, and environmental response lag, etc., and providing an efficient, low-consumption, and sustainable integrated strategy for the treatment of soil composite heavy metal pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flowchart of a heavy metal contaminated soil repair method based on biochar loading technology. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Please refer to the attached Figure 1, an embodiment of the present invention provides a method for remediating heavy metal contaminated soil based on biochar loading technology. The following will detail each step of the method of the present invention.

[0039] S1. Prepare a modified biochar matrix: pyrolyze and pickling treat biomass raw materials to obtain porous biochar, and construct loading sites on its surface.

[0040] In this embodiment, the preparation of the modified biochar matrix in step S1 includes raw material pretreatment, quantum dot embedding and surface modification, and chiral topological structure etching. The following will detail each technical feature:

[0041] Crush agricultural waste to obtain biomass particles with uniform particle size. Biomass includes raw materials rich in cellulose components such as rice husks, straws or fruit shells. Place the crushed biomass in an inert gas atmosphere for pyrolysis treatment. The inert gas is nitrogen or argon, the pyrolysis temperature range is set at 500°C to 800°C, and the constant temperature time is controlled within 1 hour to 4 hours. After pyrolysis, pickle the obtained biochar with nitric acid or hydrochloric acid solution, the concentration range is 0.05mol / L to 0.5mol / L, and the pickling time is 12 hours to 36 hours. Remove ash impurities in the biochar and activate surface functional groups, including hydroxyl, carboxyl and phenolic hydroxyl groups, through pickling, so as to enhance the anchoring ability of subsequent quantum dot loading.

[0042] Quantum dot embedding and surface modification:

[0043] Synthesize cadmium sulfide quantum dots (CdSQDs) by solvothermal method. Dissolve cadmium salt and sulfur source in ethylene glycol or deionized water at a molar ratio of 1:2 to 1:3, react at 120°C to 180°C for 2 hours to 6 hours, and obtain CdSQDs with uniform particle size distribution through centrifugal washing. Further disperse CdSQDs and graphene oxide (GO) in ethanol or water at a mass ratio of 1:3 to 1:8, and form a uniform suspension through ultrasonic treatment. Use the vacuum impregnation method to load the suspension into the pores of the pickled biochar, the vacuum degree is -0.1MPa to -0.08MPa, and the impregnation time is 2 hours to 6 hours. After loading, perform annealing treatment under inert gas protection, the annealing temperature is 200°C to 400°C, and the annealing time is 1 hour to 3 hours, so that CdSQDs and GO form a stable heterojunction structure. Confirm the crystal form and dispersion state of the quantum dots through X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization.

[0044] Chiral topological structure etching:

[0045] A femtosecond laser processing system is used to etch a helical chiral topological structure on the surface of biochar. The wavelength range of the femtosecond laser is 800 nm to 1064 nm, the pulse width is 100 fs to 500 fs, the single-pulse energy is 10 μJ to 100 μJ, and the repetition frequency is 1 kHz to 10 kHz. The laser focus position is controlled by a three-dimensional motion platform to form helical grooves with a depth of 50 nm to 500 nm and a pitch of 20 nm to 100 nm on the surface of biochar, and the chiral index (n, m) is selected from the range of (5, 2) to (9, 4). The chiral topological structure regulates the diffusion path of heavy metal ions through the geometric confinement effect.

[0046] S2. Construct a dynamic loading system based on the biochar matrix: Fix microcapsules containing the repair material at the loading sites, and the release behavior of the microcapsules is regulated by an external physical field.

[0047] In this embodiment, the construction of the dynamic loading system in step S2 includes the preparation of microcapsules, magnetic field encoding, and fixation on the biochar matrix. The following details each technical feature:

[0048] Preparation of microcapsules:

[0049] First, iron sulfide (FeS) nanoparticles are synthesized by chemical co-precipitation. The iron salt and sulfur source are dissolved in deionized water at a molar ratio of 1:1 to 1:1.5, and stirred and reacted under the protection of an inert gas. The reaction temperature is controlled at 20 °C to 60 °C, and the reaction time is 1 hour to 4 hours. Uniformly sized FeS nanoparticles are obtained after centrifugation and washing. The reducibility of FeS nanoparticles can effectively convert high-valence heavy metal ions (such as Cr 6+ 、As 5+ ) into low-toxic states (such as Cr 3+ 、As 3+ ).

[0050] Furthermore, the FeS nanoparticles and polyethyleneimine (PEI) are mixed at a mass ratio of 1:1 to 1:3 to form a chelation-reduction composite core. The molecular weight of PEI is 5 kDa to 20 kDa, and the amino functional groups on its molecular chain can bind to heavy metal ions through coordination, enhancing the fixation ability. The mixture is dispersed in a composite solution of graphene oxide (GO) and humic acid (HA), and core-shell structured microcapsules are generated by microfluidic technology. The mass ratio of GO to HA is 1:2 to 1:5. The lamellar structure of GO provides mechanical strength, and the carboxyl and phenolic hydroxyl groups of HA enhance the hydrophilicity and environmental responsiveness of the shell.

[0051] Magnetic field encoding and rupture threshold regulation:

[0052] Magnetic nanoparticles are incorporated into the microcapsule shell to achieve magnetic field responsiveness. The magnetic nanoparticles are Fe 3 O4 or CoFe 2 O 4 , and the doping amount is 3% to 10% of the total mass of the shell. The rupture threshold of the microcapsule is regulated by an external magnetic field, and its mechanical equilibrium relationship satisfies the formula:

[0053]

[0054] where M s is the saturation magnetization intensity of the magnetic particles, H is the externally applied magnetic field intensity, μ 0 is the magnetic permeability of vacuum, σ s is the yield stress of the shell material, and d is the shell thickness. By adjusting the magnetic field intensity (HH), the rupture timing of the microcapsule in the soil environment can be precisely controlled, so as to release the core repair material as needed.

[0055] Fixing the microcapsule to the biochar matrix:

[0056] Disperse the microcapsules in the spiral chiral grooves on the surface of the biochar prepared in step S1. Use ultraviolet light to initiate a cross-linking reaction to achieve stable fixation of the microcapsules. The ultraviolet light irradiation triggers the photothermal effect on the surface of graphene oxide, promoting the condensation reaction between the phenolic hydroxyl groups in humic acid and the epoxy groups of GO to form a covalent cross-linking network. The wavelength range of the ultraviolet light is 300 nm to 400 nm, and the irradiation intensity is 20 mW / cm 2 to 100 mW / cm 2 , and the curing time is 5 minutes to 30 minutes.

[0057] S3. Dynamically regulating the repair process: Real-time monitor the soil environment parameters, and adjust the physical field parameters according to the monitoring data to drive the release of the repair material and the migration and fixation of heavy metals.

[0058] In this embodiment, the dynamic regulation and repair process in step S3 includes real-time monitoring of soil parameters, optimization of the reinforcement learning model, and regulation of the field-chemistry synergistic effect. The following is a detailed description of each technical feature:

[0059] Real-time monitoring of soil parameters:

[0060] Deploy a sensor network in the polluted soil. The sensors include a pH electrode, a redox potential sensor, and a heavy metal ion selective electrode. The pH electrode adopts a glass electrode structure, and the detection range is pH 3 to pH 10; the redox potential sensor measures based on the potential difference between a platinum electrode and a reference electrode, and the measurement range covers -1000 mV to +1000 mV; the heavy metal ion selective electrode is for target heavy metals (such as Cd 2+ , Pb 2+ , Cr 6+) Design, using an ionophore-modified polymer membrane electrode, with a detection limit of 0.1 ppm to 10 ppm. The sensor network collects data at a frequency of 1 time / minute to 10 times / minute and sends the real-time data to the control module through a wireless transmission module.

[0061] Reinforcement learning model optimization:

[0062] Construct a reinforcement learning model based on the Q-learning algorithm for dynamically adjusting the magnetic field strength and ultraviolet light intensity. The state space of the model is defined as a three-dimensional vector where is the heavy metal concentration gradient; the action space is defined as a two-dimensional vector a t =[H, I UV , corresponding to the magnetic field strength and ultraviolet light intensity respectively. The reward function is designed as:

[0063] R = w 1 ·ΔC removal -w 2 ·ΔC material ;

[0064] where, ΔC removal is the amount of heavy metal removed, ΔC material is the material consumption, w 1 and w 2 are weight coefficients. The learning rate of the model is set to 0.05 to 0.2, and the discount factor is set to 0.8 to 0.95. The policy is optimized by iteratively updating the Q-value table.

[0065] Field-chemical synergistic effect regulation:

[0066] The high-frequency alternating electric field drives the directional migration of heavy metal ions through dielectrophoresis force. The frequency of the electric field is set to 1 MHz to 10 MHz, and the field strength is 10 V / m to 100 V / m, which is generated by a signal generator and a power amplifier. The dielectrophoretic migration process is described by the following partial differential equation

[0067]

[0068] where, D is the diffusion coefficient of heavy metal ions, ∈ m is the dielectric constant of the soil medium, r is the ionic hydration radius, η is the viscosity of the soil pore fluid, f CM is the Clausius-Mossotti factor.

[0069] When the detected Cr“ concentration exceeds the preset threshold, the ultraviolet light source is activated to drive the photocatalytic reduction reaction of CdS quantum dots. The ultraviolet light wavelength is set to 300 nm to 400 nm, and the light intensity is 10 mW / cm 2 to 50 mW / cm 2。The photo-generated electrons transfer from the conduction band of CdS to Cr 6+ , triggering a reduction reaction:

[0070]

[0071] S4. Regeneration and recovery: After the repair is completed, the function of the load system is restored by triggering the self-healing mechanism, and heavy metals and biochar are recovered.

[0072] In this embodiment, the regeneration and recovery process of step S4 includes activation of the self-healing mechanism, regeneration of biochar, and recovery of heavy metals. The following is a detailed description of each technical feature:

[0073] Activation of the self-healing mechanism:

[0074] When the sensor network detects that the oxidation rate of FeS nanoparticles in the dynamic load system exceeds the preset threshold, the microcapsule shell is irradiated with ultraviolet light. The wavelength of the ultraviolet light is selected from 250 nm to 300 nm, and the light intensity range covers 50 mW / cm 2 to 150 mW / cm 2 . Ultraviolet photons excite the photosensitive groups in the graphene oxide-humic acid composite shell, triggering a click chemical reaction between thiol (-SH) and alkene (C=C):

[0075]

[0076] This reaction proceeds through a free radical chain mechanism to repair the cracks in the microcapsule shell caused by mechanical stress or chemical corrosion. The repaired microcapsule restores its controlled release function of the loaded material and re-participates in the heavy metal repair process.

[0077] Regeneration of biochar and recovery of heavy metals:

[0078] The biochar matrix that has completed the repair task is taken out of the soil and subjected to pyrolysis oxidation treatment. The pyrolysis process is carried out in an air atmosphere, the temperature is set at 500 °C to 800 °C, and the holding time is 0.5 hour to 2 hours. Under high temperature conditions, the CdS quantum dots loaded in the pores of the biochar are oxidized to CdO, and the reaction equation is:

[0079]

[0080] The pyrolyzed biochar is pulverized and immersed in an acidic solution. 0.5 mol / L to 2 mol / L hydrochloric acid is used as the leaching agent, and it is treated under stirring conditions for 1 hour to 4 hours to convert CdO into soluble Cd 2+ ions. The leachate is separated by filtration, and Cd is recovered by electrolytic deposition or chemical precipitation 2+。The regenerated biochar is washed with deionized water until neutral, and after drying, it re-enters the modification process of step S1 to achieve recycling.

[0081] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for remediating heavy metal contaminated soil based on biochar loading technology, characterized in that: The following steps are involved: S1. Preparation of modified biochar matrix: Pyrolysis and acid washing of biomass raw materials to obtain porous biochar, and constructing loading sites on its surface; S2. constructing a dynamic loading system based on the biochar matrix: fixing microcapsules containing repair materials at the loading sites, and regulating the release behavior of the microcapsules by an external physical field; S3. Dynamically regulate the remediation process: monitor soil environmental parameters in real time, adjust the physical field parameters according to the monitoring data, drive the release of remediation materials and the migration and fixation of heavy metals; S4. Regeneration and recycling: After the repair is completed, the load system function is restored by triggering the self-repair mechanism, and the heavy metals and biochar are recycled.

2. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In step S1: The pyrolysis is carried out in an inert gas atmosphere at a temperature of 500-800° C. for a constant temperature time of 1-4 h; The pickling adopts nitric acid or hydrochloric acid solution with a concentration of 0.05-0.5 mol / L and a treatment time of 12-36 hours.

3. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In the step S1, a spiral chiral topological structure is formed on the surface of the biochar by laser etching, the chiral index is (n, m) = (5, 2) - (9, 4), the groove depth is 50-500nm, and the spacing is 20-100nm.

4. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In step S2: The microcapsule comprises a core and an outer shell, wherein the core is a mixture of FeS nanoparticles and a polymer, and the outer shell is a graphene oxide-humic acid composite film doped with magnetic nanoparticles; The release threshold of the microcapsule satisfies the formula: Among them, M s is the saturation magnetization of the magnetic nanoparticles, H is the external magnetic field strength, μ0 is the vacuum permeability, σ s is the shell yield stress, and d is the shell thickness.

5. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: The microcapsules are fixed in the spiral chiral grooves of the biochar by UV curing, the UV wavelength is 300-400nm, and the intensity is 30-100mW / cm 2 , the curing time is 5-20min.

6. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In step S3, the physical field parameter adjustment is implemented by a reinforcement learning model, which takes real-time data of soil pH, redox potential and heavy metal concentration as input and magnetic field intensity and ultraviolet light intensity as output, wherein: The reinforcement learning model is a Q-learning algorithm, and its action space is defined as the magnetic field intensity range 0-200kA / m and the ultraviolet light intensity range 0-100mW / cm 2 ; The reward function of the model is the weighted difference between the amount of heavy metals removed and the amount of material consumed.

7. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In step S3, the migration of heavy metals is achieved by dielectrophoresis force driven by a high-frequency alternating electric field, and the migration equation satisfies: Where C is the heavy metal concentration, D is the diffusion coefficient, ∈ m is the dielectric constant of the medium, r is the particle radius, η is the viscosity, f CM is the Clausius-Mossotti factor.

8. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In step S4, the self-repair mechanism is a thiol-ene click chemistry reaction triggered by ultraviolet light, and the reaction formula is:

9. The method for remediating heavy metal contaminated soil based on biochar loading technology according to claim 1, characterized in that: In step S4, heavy metal recovery is achieved by pyrolysis oxidation and acid leaching, wherein the pyrolysis temperature is 500-800° C. and the acid leaching solution is 0.5-2 mol / L hydrochloric acid.

Images