Low-temperature plasma-microorganism synergistic tailings harmless treatment method

Abstract

The application relates to the field of solid waste harmless treatment, and discloses a low-temperature plasma-microorganism synergistic tailing sand harmless treatment method. In view of the problems that the plasma is easy to damage the microorganism, the two reactions are mutually inhibited, and the material utilization rate is low in the existing synergistic technology, the gradient functionalized microorganism-carrier composite is adopted to realize the spatial isolation of the catalyst and the microorganism, the space-time phase separation treatment mode is constructed through the rotatable material tray, the mixed material periodically alternates to experience the plasma activation and the microorganism mineralization process, the two-way material circulation is realized by combining the gas circulation closed loop regulation, the tailing sand and the carrier are separated after treatment, and the carrier is activated and regenerated for recycling. The application realizes the stable symbiosis and synergy of the plasma and the microorganism, eliminates the mutual inhibition of the two reactions, improves the material utilization rate, reduces the operation cost, and is suitable for the harmless treatment of various heavy metal and sulfide pollution tailing sands.

Description

Technical Field

[0001] This invention relates to the field of solid waste harmless treatment technology, specifically a low-temperature plasma-microorganism synergistic tailings harmless treatment method. Background Technology

[0002] This invention relates to the field of harmless treatment technology for solid waste from mines. Mining processes generate large quantities of tailings, which typically contain toxic and harmful pollutants such as heavy metals and sulfides. Long-term open-air storage of tailings can cause soil, water, and air pollution through rainwater leaching and windblown dust, threatening the surrounding ecological environment and human health. The safe and harmless disposal of tailings has become a critical issue urgently needing to be addressed for the sustainable development of the mining industry.

[0003] Currently, tailings harmless treatment technologies mainly include solidification and stabilization, chemical oxidation, and microbial remediation. Among these, low-temperature plasma and microbial synergistic treatment technology combines the advantages of rapid plasma reaction and long-term stability of microbial remediation, and is gradually becoming a research direction in the field of tailings treatment. Existing synergistic treatment technologies mostly adopt a structural design that directly couples plasma and microorganisms in the same cavity, allowing tailings to complete the pollutant activation and mineralization processes sequentially within the same reaction system.

[0004] Existing co-processing technologies cannot achieve effective structural isolation between plasma-active species and microorganisms. The high-energy particles and active free radicals generated by plasma can damage the cell structure and metabolic system of microorganisms, leading to a rapid decline in microbial activity or even inactivation. This affects the stability and sustainability of the co-processing effect, limiting the industrial application of this technology. Summary of the Invention

[0005] The first aspect of this invention provides a low-temperature plasma-microorganism synergistic tailings harmless treatment method. Addressing the problems of plasma easily damaging microorganisms, mutual inhibition between plasma and microbial mineralization reactions, and low material utilization rates in existing low-temperature plasma and microbial synergistic tailings treatment technologies, this method constructs a triple synergistic treatment system based on the spatial isolation effect of gradient functionalized carriers, the spatiotemporal phase separation synergistic effect of plasma and microorganisms, and the material closed-loop symbiotic effect of gas circulation, thereby achieving the oxidation of sulfides and the stabilization of heavy metals in tailings.

[0006] This method first prepares a gradient-functionalized microbial-carrier composite. A porous biochar substrate with a hierarchical pore structure is prepared using agricultural waste as raw material. The porous biochar substrate is then modified with surface-to-internal gradient functional groups to construct a gradient functional group distribution with hydrophobic macropores and hydrophilic mesopores in the outer surface and macropores. Based on the spatial barriers and interfacial differences formed by the gradient functional groups, ferric oxide catalysts are selectively loaded on the outer surface of the porous biochar and the inner walls of the macropores. Composite functional microbial communities are directionally immobilized in the internal mesopores and micropores, forming a spatial separation structure between the catalyst and the microorganisms. This spatial separation structure prevents plasma-active species from entering the internal pores, avoiding direct damage to the microorganisms from the plasma.

[0007] This method involves crushing, screening, multi-stage impurity removal, and moisture content adjustment of the tailings to be treated. The pretreated tailings are then uniformly mixed with a gradient functionalized microbial-carrier composite at a predetermined ratio to obtain a mixture. This mixture is fed into a vertical, flat-plate dielectric barrier discharge plasma reactor. A rotating material tray allows the mixture to periodically alternate between the plasma-interacting zone and the non-plasma-interacting zone for spatiotemporal phase separation and synergistic treatment. In the plasma-interacting zone, high-energy electrons, reactive oxygen species, and reactive nitrogen species generated activate stable pollutants in the tailings, converting difficult-to-leach bound heavy metals into ionic reactive heavy metals and oxidizing metal sulfides to generate soluble metal sulfates. In the non-plasma-interacting zone, aerobic microorganisms in the mesoporous channels and anaerobic microorganisms in the microporous channels within the carrier utilize the intermediate products generated by the plasma reaction for metabolic activities, converting reactive pollutants into stable sulfide, carbonate, and phosphate precipitates.

[0008] This method collects microbial metabolic gases generated in the non-plasma interaction zone, purifies them in two stages, mixes them with compressed air in a specific ratio, and reuses them as working gas in the plasma reactor. Hydrogen sulfide in the mixed gas decomposes in the plasma field to generate highly reactive sulfur free radicals, enhancing the oxidation reaction of metal sulfides. Online monitoring of gas phase composition changes allows for dynamic adjustment of the gas mixing ratio and plasma operating parameters, ensuring a dynamic balance between plasma reaction and microbial metabolism, achieving a two-way closed-loop material circulation and synergistic effect.

[0009] After processing, the tailings and gradient functionalized microorganism-carrier complexes are separated by vibrating sieving. The separated gradient functionalized microorganism-carrier complexes are then sterilely cleaned and activated to restore the catalytic activity of the carriers and the metabolic activity of the microorganisms before being returned to the material mixing process for recycling.

[0010] A second aspect of the present invention provides a treatment system for the aforementioned low-temperature plasma-microorganism synergistic tailings harmless treatment method. The treatment system includes a gradient functionalized microorganism-carrier composite, a vertical flat-plate dielectric barrier discharge plasma reactor unit, a material conveying and spatiotemporal phase separation realization unit, a gas circulation and closed-loop control unit, and a material separation and carrier regeneration unit.

[0011] The vertical, flat-plate dielectric barrier discharge plasma reactor unit employs a structure with parallel upper and lower electrodes covered by a quartz dielectric plate, and the electrode spacing is adjustable. The reactor's internal space is divided into a plasma interaction zone and a non-plasma interaction zone. The volume of the non-plasma interaction zone is 3-5 times that of the plasma interaction zone, matching the ratio of plasma interaction time to microbial metabolism time. The pulsed power supply system is rigidly synchronized with the material conveying unit, initiating discharge only when the material tank is within the plasma interaction zone.

[0012] The material conveying and spatiotemporal phase separation unit includes a rotatable material tray, a drive control system, and an infeed / outfeed system. Multiple detachable material troughs are evenly distributed on the rotatable material tray, with ventilation holes at the bottom of the troughs to promote mass transfer of reactant gases within the material layer. The drive control system rotates the tray via a servo motor, precisely adjusting the residence time ratio of materials in the plasma-enhanced and non-plasma-enhanced zones, achieving temporal separation and spatial parallelism of plasma activation and microbial mineralization.

[0013] The gas circulation and closed-loop control unit includes a gas collection hood, a two-stage gas purification device, a static gas mixer, an oil-free diaphragm gas pump, an online gas phase component detection device, and a closed-loop controller. The gas collection hood covers the upper space of the non-plasma interaction zone, collecting microbial metabolic gases. The two-stage gas purification device is connected in series to remove solid impurities and trace organic impurities from the gas, while retaining target reusable components such as hydrogen sulfide and carbon dioxide. The closed-loop controller adjusts the gas mixing ratio and plasma operating parameters in real time based on the gas phase component detection results to maintain a dynamic balance between plasma reaction and microbial metabolism.

[0014] The material separation and carrier regeneration unit includes a double-layer linear vibrating screen and a carrier activation and cultivation device. The double-layer linear vibrating screen separates the treated tailings from the gradient functionalized microorganism-carrier complex through graded screening. The carrier activation and cultivation device provides nutrients and environmental conditions for the separated gradient functionalized microorganism-carrier complex, restoring the metabolic activity of the microorganisms and enabling the carrier to be recycled and reused.

[0015] This invention provides a low-temperature plasma-microorganism synergistic tailings harmless treatment method. It has the following beneficial effects: 1. This invention constructs a gradient functionalized microbial-carrier complex by loading ferric oxide catalyst on the outer surface and macropores, and fixing composite functional bacterial communities in the internal mesopores and micropores. By utilizing the limited interaction distance of plasma active species, spatial isolation between the catalyst and microorganisms is achieved, effectively avoiding the problem of microbial inactivation caused by direct plasma contact in traditional synergistic technologies, and realizing long-term stable symbiosis between plasma and microorganisms.

[0016] 2. This invention divides the interior of the reactor into a plasma-activated zone and a non-plasma-activated zone by a rotatable material tray, allowing the mixed materials to periodically undergo plasma activation and microbial mineralization processes. This simultaneously achieves temporal separation and spatial parallelism of the two reactions, eliminating mutual inhibition between the plasma reaction and the microbial mineralization reaction, and improving the overall efficiency of tailings harmless treatment.

[0017] 3. This invention collects microbial metabolic gases through a gas circulation and closed-loop control unit and reuses them in the plasma reactor, realizing bidirectional material exchange between plasma reaction products and microbial metabolic products. At the same time, it achieves the reuse of gradient functionalized microbial-carrier complexes through carrier separation and activation regeneration processes, reducing the operating cost and material consumption of tailings harmless treatment. Attached Figure Description

[0018] Figure 1 This is a system framework diagram of the present invention; Figure 2 This is a flowchart of the method of the present invention. Detailed Implementation

[0019] The technical solutions in 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.

[0020] See attached document Figure 1The low-temperature plasma-microorganism synergistic tailings harmless treatment system of the present invention consists of a gradient functionalized microorganism-carrier composite, a pulse-modulated dielectric barrier discharge plasma reactor, a rotatable material tray unit, a gas circulation and closed-loop control unit, a tail gas treatment unit, and a material separation and carrier regeneration unit. The gradient functionalized microorganism-carrier composite serves as the reaction core, simultaneously undertaking three functions: plasma catalysis, microbial immobilization, and heavy metal adsorption, corresponding to an integrated gradient structure of external surface catalysis, internal biological metabolism, and pore adsorption. The pulse-modulated dielectric barrier discharge plasma reactor provides plasma active species to activate stable pollutants in the tailings. The rotatable material tray unit enables the periodic switching of materials between the plasma interaction zone and the non-plasma interaction zone, forming a temporally and spatially coupled phase-separated treatment mode, i.e., plasma activation and microbial mineralization reactions occur simultaneously in different spaces, and the same material undergoes two reaction stages sequentially at different times. The gas circulation and closed-loop control unit collects microbial metabolic gases and reuses them in the plasma reactor, achieving a bidirectional material closed-loop cycle: the microbial metabolic gases are mixed with compressed air and used as the plasma working gas, while the plasma reaction products simultaneously serve as the carbon and nitrogen sources for microbial metabolism. The exhaust gas treatment unit renders unreacted exhaust gas harmless. The material separation and carrier regeneration unit separates the treated tailings from the carrier and allows for the reuse of the carrier.

[0021] The gradient-functionalized microorganism-carrier complex uses porous biochar with surface-to-internal gradient functionalization as a substrate. Iron-based oxide catalysts are loaded onto the outer surface and macropores, while the internal mesopores and micropores immobilize the composite functional microbial community. The pulse-modulated dielectric barrier discharge plasma reactor adopts a vertical flat-plate structure, with quartz dielectric plates covering the upper and lower electrode surfaces. The electrode spacing can be adjusted via a lifting mechanism. A rotatable material tray unit is located inside the reactor between the upper and lower electrodes, driven by a servo motor. Multiple detachable material troughs are set on the tray surface, with the depth of the troughs matching the preset material thickness. The gas circulation and closed-loop control unit includes a gas collection hood, a gas purification device, a gas mixer, a gas pump, and a gas phase component detection element. The gas collection hood is located above the non-plasma interaction zone, and the gas phase component detection element is installed in the gas collection pipeline for real-time monitoring of changes in the composition of microbial metabolic gases. The tail gas treatment unit consists of an ozone decomposition catalyst bed and an alkaline absorption tower connected in series. The material separation and carrier regeneration unit includes a vibrating sieve device and a carrier activation and cultivation device.

[0022] See attached document Figure 2 The workflow of the low-temperature plasma-microorganism synergistic tailings harmless treatment method provided in this embodiment of the invention is as follows: S1. Prepare gradient-functionalized porous biochar support, modify the support with surface-internal gradient functional groups, selectively load iron-based oxide catalysts, and then fix the domesticated composite functional microbial community to obtain a gradient-functionalized microbial-support composite.

[0023] S2. The tailings to be treated are crushed and screened to remove large impurities. The pretreated tailings are then mixed with gradient functionalized microorganism-carrier complex in a preset mass ratio to obtain a mixture.

[0024] S3. Spread the mixture evenly in the material trough of the rotatable material tray, control the thickness of the spread, start the servo motor to drive the tray to rotate, so that the material alternates periodically between the plasma action zone and the non-plasma action zone, and the switching cycle is synchronized with the plasma pulse cycle.

[0025] S4. Start the pulse-modulated plasma power supply, adjust the pulse voltage, pulse frequency and duty cycle parameters to generate dielectric barrier discharge in the plasma interaction zone, and perform stable-state pollutant activation treatment on the mixed materials entering the plasma interaction zone.

[0026] S5. After the mixture enters the non-plasma interaction zone, the complex functional microbial community in the internal pores of the carrier uses the intermediate products generated by the plasma reaction to carry out metabolic activities, including carbon dioxide, nitrogen oxides and partially oxidized sulfide intermediate products, to biomineralize active pollutants.

[0027] S6. The gas collection hood collects the gas produced by microbial metabolism in the non-plasma interaction zone. After the gas purification device removes dust and impurities, it is sent to the gas mixer to be mixed with compressed air in a preset ratio. The mixed gas is sent to the plasma reactor as the working gas. The hydrogen sulfide component in the mixed gas decomposes in the plasma field to produce active sulfur species, which enhances the sulfide oxidation reaction.

[0028] S7. The unreacted tail gas discharged from the plasma reactor enters the tail gas treatment unit, and after ozone decomposition and alkaline absorption treatment, it meets the emission standards.

[0029] S8. Repeat the alternating treatment process from S4 to S7 until the leaching concentration of heavy metals and the sulfide content in the tailings meet the relevant national standards.

[0030] S9. After the treatment is completed, the mixture is taken out of the reactor and sent to a vibrating screen to separate the gradient functionalized microorganism-carrier complex from the treated tailings.

[0031] S10. The separated gradient functionalized microorganism-carrier complex is sent to the carrier activation culture device, supplemented with nutrients and activated culture, and then returned to step S2 for reuse.

[0032] S11. The treated tailings are utilized for resource recovery, including the preparation of building materials, mine backfilling, or land reclamation.

[0033] The specific implementation methods of servo motor drive control, pulse power supply parameter adjustment, online detection of gas phase components, and gas flow control are well-known technologies in this field and will not be elaborated here.

[0034] The porous biochar substrate was prepared using agricultural waste as raw material. Agricultural waste includes corn stalks, rice stalks, and wheat stalks. These raw materials are characterized by high carbon content, well-developed natural porous structures, and wide availability, making them suitable as substrate materials for gradient functionalization carriers. The agricultural waste was washed three times with deionized water to remove surface-adhered soil and impurities. The washed agricultural waste was then dried in a forced-air drying oven to constant weight. The dried agricultural waste was crushed using a jaw crusher, and the crushed material was sieved using a standard sieve to collect particles of 20-40 mesh. Particles within this size range exhibit uniform heat and mass transfer during pyrolysis, enabling the formation of a uniformly distributed initial pore structure.

[0035] The sieved particles were transferred to a tube furnace. High-purity nitrogen was introduced into the tube furnace as a protective gas, with the nitrogen flow rate controlled at 100-200 mL / min. The temperature of the tube furnace was increased to 500-700℃ at a rate of 5-10℃ / min and held at the target temperature for 1-3 hours. This pyrolysis temperature range allows for the complete carbonization of agricultural waste while retaining sufficient surface functional groups to prevent pore collapse due to high temperatures. After the holding period, the tube furnace was allowed to cool naturally to room temperature under nitrogen protection. The cooled pyrolysis products were then ground using a ball mill. The ground material was sieved using a standard sieve to collect 60-80 mesh particles, yielding crude biochar.

[0036] Crude biochar was subjected to acid treatment. The crude biochar was placed in a 1 mol / L hydrochloric acid solution with a solid-liquid ratio controlled at 1:10. Acid treatment was carried out at a constant temperature of 60℃, with a stirring rate controlled at 200 r / min, for 4-6 hours. Acid treatment was used to remove ash, soluble metal ions, and alkaline impurities from the crude biochar and to unclog blocked initial pores. After acid treatment, the biochar was washed with deionized water until the pH of the filtrate reached neutral. The washed biochar was then dried in a forced-air drying oven to constant weight.

[0037] The acid-treated biochar underwent alkali treatment. The biochar was placed in a 2 mol / L sodium hydroxide solution with a solid-liquid ratio controlled at 1:8. The alkali treatment was carried out at a constant temperature of 80℃, with a stirring rate controlled at 200 r / min, for 2-4 hours. The alkali treatment, through etching, generated numerous new mesopores and micropores on the surface and inside the biochar, achieving directional control of the pore structure and introducing active functional groups such as hydroxyl groups. After alkali treatment, the biochar was washed with deionized water until the pH of the filtrate reached neutral. The washed biochar was then dried in a forced-air drying oven to constant weight, yielding a porous biochar substrate.

[0038] Porous biochar substrates possess a hierarchical pore structure, classified according to the International Union of Pure and Applied Chemistry (IUPAC) standards, including macropores with a pore size greater than 50 nm, mesopores with a pore size of 2-50 nm, and micropores with a pore size less than 2 nm. This hierarchical pore structure provides a structural basis for subsequent gradient functional group modification, catalyst loading, and microbial immobilization. Macropores are used for loading iron-based oxide catalysts and transporting reactant gases. Mesopores are used for immobilizing aerobic microorganisms. Micropores are used for immobilizing anaerobic microorganisms.

[0039] Porous biochar substrates were modified with surface-to-internal gradient functional groups to create a gradient functional group distribution on the outer surface and in the macropores (hydrophobic), mesopores and micropores (hydrophilic). This provides specific binding sites for the selective loading of iron-based oxide catalysts and the directional immobilization of complex functional microbial communities. Gradient functional group modification is the core structural basis for achieving spatial isolation between the catalyst and microorganisms and preventing plasma damage to the microorganisms. The specific implementation steps are as follows: S1. Hydrophobic Modification of the Outer Surface and Macropores. The porous biochar substrate was placed in a vacuum impregnation apparatus, and a vacuum was drawn to an absolute pressure below 1 kPa. This vacuum environment removes air from the porous biochar pores, ensuring uniform reagent entry into the macropores. A 5%-10% solution of octadecyltrichlorosilane in hexane was injected. The molecular dynamic diameter of octadecyltrichlorosilane is approximately 2.6 nm, larger than the maximum pore size of mesopores and micropores (2 nm), preventing it from entering the mesopores and micropores. The reaction was carried out at a constant temperature of 25-40℃ for 2-4 hours. Octadecyltrichlorosilane can only undergo silanization with hydroxyl groups on the outer surface and the inner walls of the macropores, grafting long-chain alkyl functional groups. After the reaction, the porous biochar was washed three times with hexane to remove unreacted octadecyltrichlorosilane in hexane solution, and then dried in a forced-air drying oven to constant weight.

[0040] S2. Mesoporous and Microporous Channel Template Blocking. The hydrophobically modified porous biochar is immersed in a 10%-20% aqueous solution of polyethylene glycol 2000 and ultrasonically impregnated at a constant temperature of 25-35℃ for 1-2 hours. The molecular dynamic diameter of polyethylene glycol 2000 is approximately 1.8 nm, allowing it to freely enter mesoporous and microporous channels, but it cannot pass through the hydrophobic barrier of the macroporous channel inner wall. After hydrophobic modification, the outer surface and the inner wall of the macroporous channels become hydrophobic. Water-soluble polyethylene glycol 2000 molecules cannot adsorb on the hydrophobic surface, therefore they can only enter the internal mesoporous and microporous channels, adsorbing onto the hydroxyl groups on the inner walls of the mesoporous and microporous channels, achieving selective blockage of the internal pores. After impregnation, the porous biochar is removed, and excess solution is blotted off with filter paper.

[0041] S3. Hydrophilic Modification of Mesoporous and Microporous Channels. The template-sealed porous biochar was placed in a reaction vessel, and a 5%-15% aqueous solution of acrylic acid and ammonium persulfate initiator were added. The amount of ammonium persulfate was 1%-3% of the mass of acrylic acid. The pH of the reaction system was adjusted to 3-4, and high-purity nitrogen was introduced to purge oxygen from the reaction vessel. The reaction was carried out at a constant temperature of 50-70℃ for 3-6 hours. The hydroxyl groups on the outer surface and the inner walls of the macropores were completely reacted by the octadecyltrichlorosilane-hexane solution, leaving no active sites for acrylic acid grafting. The hydroxyl groups on the inner walls of the mesopores and micropores not covered by polyethylene glycol 2000 molecules could undergo free radical polymerization with acrylic acid, grafting carboxyl functional groups. After the reaction was complete, the porous biochar was washed three times with deionized water to remove unreacted acrylic acid monomers and ammonium persulfate initiator.

[0042] S4. Template molecule elution. The hydrophilically modified porous biochar was placed in a solution of anhydrous ethanol and deionized water at a volume ratio of 1:1 and refluxed for 4-6 hours to remove polyethylene glycol 2000 template molecules adsorbed on the inner walls of mesopores and micropores. The eluent was changed every 2 hours during elution until the UV absorbance of the eluent at 280 nm was below 0.01. After elution, the porous biochar was washed with deionized water until the filtrate was neutral and dried in a forced-air drying oven to constant weight to obtain porous biochar modified with surface-internal gradient functional groups.

[0043] Porous biochar modified with a surface-to-internal gradient functional group exhibits a functional group distribution characterized by hydrophobicity on the outer surface and hydrophilicity on the inner surface. The hydrophobic functional groups on the outer surface and the inner walls of the macropores prevent water-soluble iron salt precursors from entering the internal pores, enabling selective loading of iron-based oxide catalysts only on the outer surface and in the macropores; simultaneously, they prevent microorganisms from attaching to the outer surface, avoiding direct plasma damage to microorganisms. The hydrophilic carboxyl functional groups on the inner walls of the mesopores and micropores provide covalent binding sites for complex functional bacterial communities, enabling the directional immobilization of microorganisms in the internal pores. The formation of the gradient functional group distribution can be verified by measuring the water contact angles on the outer surface and internal pores of the porous biochar using a contact angle meter.

[0044] Porous biochar modified with surface-to-internal gradient functional groups was selectively gradient-loaded with iron-based oxide catalysts, achieving a uniform distribution of ferric oxide nanoparticles only on the outer surface of the porous biochar and the inner walls of the macropores. This selective gradient loading is achieved based on the spatial barriers and interfacial differences formed by the gradient functional groups, providing heterogeneous catalytic active sites for plasma reactions while preventing the catalyst from entering the internal pores and affecting microbial immobilization and metabolic activity. The specific implementation steps are as follows: S1. Preparation and Selective Impregnation of Iron Salt Precursor Solution. A 0.5-1.5 mol / L aqueous solution of ferric nitrate nonahydrate was prepared as the catalyst precursor. Porous biochar modified with surface-internal gradient functional groups was immersed in the ferric nitrate nonahydrate aqueous solution and allowed to stand at a constant temperature of 25-35℃ for 1-3 hours. The hydrophobic long-chain alkyl groups on the outer surface of the porous biochar and the inner walls of the macropores form a hydrophobic barrier, preventing water-soluble ferric nitrate nonahydrate molecules from entering the internal mesopores and micropores; iron ions can only undergo physical adsorption at the solid-liquid interface within the macropores, achieving selective loading. After impregnation, the porous biochar was removed and blotted dry with filter paper until there was no obvious liquid film on the surface of the porous biochar and no adhesion between particles. In other embodiments, the iron salt precursor can also be a soluble iron salt such as ferric chloride or ferric sulfate, which can also form a corresponding iron-based oxide catalyst after similar calcination treatment.

[0045] S2. Low-temperature drying treatment. The porous biochar after adsorbing iron ions is placed in a forced-air drying oven and dried at a constant temperature of 60-80℃ for 12-24 hours. This temperature range can slowly remove moisture and avoid rapid evaporation of moisture, which would cause the iron salt precursor to agglomerate at the pore inlet, ensuring that the precursor is uniformly deposited on the outer surface of the porous biochar and the inner wall of the macropores.

[0046] S3. Inert Atmosphere Calcination and Decomposition. The dried porous biochar was transferred to a tube furnace, and high-purity nitrogen was introduced as a protective gas, with the nitrogen flow rate controlled at 100-150 mL / min. The tube furnace was heated to 300-400℃ at a rate of 3-5℃ / min and held at the target temperature for 2-4 hours to completely decompose the ferric nitrate nonahydrate precursor into ferric oxide nanoparticles. This heating rate prevents the gas impact generated by the rapid decomposition of the precursor from causing the nanoparticles to detach, and this calcination temperature range ensures the complete decomposition of ferric nitrate while avoiding the sintering and growth of ferric oxide nanoparticles due to high temperature. After the holding period, the tube furnace was naturally cooled to room temperature under nitrogen protection. After calcination, the porous biochar was washed three times with deionized water to remove undecomposed soluble iron salts and byproducts generated during calcination. It was then dried in a forced-air drying oven to constant weight to obtain porous biochar loaded with an iron-based oxide catalyst. The chemical reactions that occurred during the calcination process are as follows: In the formula: It is a precursor to ferric nitrate nonahydrate; It is a supported ferric oxide catalyst; The nitrogen dioxide gas produced during decomposition; For the oxygen produced by decomposition; The water vapor produced by decomposition.

[0047] In porous biochar supported on iron-based oxide catalysts, the particle size of ferric oxide nanoparticles is controlled within the range of 10-50 nm. Ferric oxide possesses high catalytic activity, good stability, and low cost, making it suitable as a heterogeneous catalyst for low-temperature plasma reactions. Ferric oxide nanoparticles within this particle size range have a large specific surface area, providing sufficient catalytic active sites without clogging macropores and affecting gas mass transfer. The loading of the ferric oxide catalyst can be controlled by adjusting the concentration of the ferric nitrate nonahydrate aqueous solution and the number of impregnation cycles. The loading of the ferric oxide catalyst is controlled between 5% and 15% (mass fraction). Too low a loading will not provide sufficient catalytic activity, while too high a loading will lead to nanoparticle aggregation and reduced catalytic efficiency. The ferric oxide catalyst can catalyze the generation of reactive oxygen and nitrogen species during plasma reactions, enhancing the oxidation of sulfides and the activation of stable heavy metals in tailings. The ferric oxide catalyst is only distributed on the outer surface of the porous biochar and the inner walls of the macropores, and does not enter the internal mesopores and micropores, therefore it will not have a toxic effect on subsequently immobilized microorganisms.

[0048] Porous biochar supported on iron-based oxide catalysts was used for screening, domestication, and gradient immobilization of multifunctional microbial communities, constructing an aerobic-anaerobic gradient micro-ecosystem matching the pore structure of the support. The gradient immobilization of the multifunctional microbial communities, along with the surface-internal gradient functional group modification of the support and the selective gradient loading of the iron-based oxide catalyst, constitutes the triple gradient functional structure of the support, a core prerequisite for achieving symbiotic synergy between plasma and microorganisms. The multifunctional microbial communities are responsible for converting plasma-activated active pollutants into stable mineral phases, while gradient immobilization enables spatial isolation between microorganisms and the catalyst, preventing direct damage to microorganisms from the plasma. The specific implementation steps are as follows: S1. Isolation and Screening of Functional Microorganisms. Environmental samples were collected from topsoil of heavy metal-contaminated mines, acidic mine wastewater, and leachate from tailings dumps. Environmental samples were serially diluted and spread onto corresponding selective media and incubated at constant temperature. Single colonies were picked and streaked at least three times for purification to obtain pure strains. Sulfur-oxidizing bacteria were cultured on Starkey medium at 30℃; iron-oxidizing bacteria were cultured on 9K medium at 30℃; sulfate-reducing bacteria were cultured on Postgate medium in an anaerobic incubator at 35℃; and heavy metal-tolerant bacteria were cultured on LB medium supplemented with the target heavy metal ions at 30℃. The screened functional microorganisms included sulfur-oxidizing bacteria, iron-oxidizing bacteria, sulfate-reducing bacteria, and heavy metal-tolerant bacteria. Sulfur-oxidizing bacteria are responsible for oxidizing sulfides, iron-oxidizing bacteria are responsible for oxidizing ferrous ions and promoting heavy metal co-precipitation, sulfate-reducing bacteria are responsible for reducing sulfates and generating metal sulfide precipitates, and heavy metal-tolerant bacteria are responsible for stabilizing heavy metals through biosorption and biomineralization.

[0049] S2. Acclimation of the Composite Functional Microbial Community. The isolated and purified single bacterial strains were mixed according to their colony count ratio to form an initial composite functional microbial community. The colony count ratio of sulfur-oxidizing bacteria, iron-oxidizing bacteria, sulfate-reducing bacteria, and heavy metal-tolerant bacteria was (2-3):(1-2):(1-2):(1-2). This ratio ensures a balance between aerobic oxidation and anaerobic reduction processes, avoiding the accumulation of intermediate products that inhibit microbial activity. Acclimation was carried out stepwise using a modified 9K inorganic salt medium supplemented with heavy metal ions and sulfides. During the acclimation process, the concentration of heavy metal ions and sulfides in the medium was gradually increased. Each acclimation cycle was 3-5 days, and the inoculum size for each generation was 5%-10%. After 30-60 generations of continuous acclimation, a composite functional microbial community with high adaptability to tailings pollution was obtained. After acclimation, the composite functional microbial community was inoculated into liquid culture medium for expansion culture. The cells were collected at the late logarithmic growth phase, washed three times with sterile physiological saline, and resuspended to prepare a bacterial suspension.

[0050] S3. Activation of functional groups in the internal pores of the support. Porous biochar loaded with iron-based oxide catalyst was placed in a phosphate buffer solution with a pH of 7.2-7.4, with a solid-liquid ratio of 1:10. Glutaraldehyde crosslinking agent was added at a mass concentration of 2%-5%. Activation was performed by shaking in a constant-temperature shaker at 25-30℃ and 120 rpm for 1-2 hours. The glutaraldehyde crosslinking reaction is mild and will not damage the cell structure and metabolic activity of microorganisms. During activation, the carboxyl functional groups on the inner walls of the mesopores and micropores inside the support react with glutaraldehyde, transforming into aldehyde active sites. The outer surface of the support and the inner walls of the macropores are hydrophobic long-chain alkyl groups without carboxyl functional groups, therefore no activation reaction occurs. After activation, the porous biochar was washed three times with sterile phosphate buffer solution to remove unreacted glutaraldehyde.

[0051] S4. Gradient fixation of complex functional bacterial communities. Activated porous biochar was added to the prepared bacterial suspension at a solid-liquid ratio of 1:20, and the concentration of the bacterial suspension was 10. 8 -10 9 CFU / mL. Cultured in a constant-temperature shaker at 30℃ and 150 rpm for 24-48 h. The 150 rpm shaking rate ensures sufficient contact between the bacterial suspension and the carrier without disrupting the carrier's pore structure. The outer surface of the carrier and the inner walls of the macropores are hydrophobic and loaded with iron-based oxide catalysts, preventing microorganisms from attaching and growing in these areas. The inner walls of the mesopores and micropores within the carrier contain aldehyde active sites, allowing microorganisms to bind to the pore walls via covalent bonds. The larger pore size of the mesopores allows for ample oxygen diffusion, suitable for the growth of aerobic sulfur-oxidizing and iron-oxidizing bacteria; the smaller pore size of the micropores hinders oxygen diffusion, creating a natural anaerobic microenvironment suitable for the growth of anaerobic sulfate-reducing bacteria. No inert gas is required during cultivation; the natural oxygen gradient within the carrier pores forms the aerobic-anaerobic zone. After cultivation, the porous biochar is washed three times with sterile physiological saline to remove unfixed free microorganisms. Plate counting is performed on the carrier surface; the number of free microorganisms on the carrier surface is less than 10. 3 CFU / g proved that the microorganisms were immobilized only in the internal pores. This ultimately yielded a gradient-functionalized microorganism-carrier complex.

[0052] In the gradient-functionalized microbial-carrier complex, aerobic microorganisms are mainly distributed in mesoporous channels, while anaerobic microorganisms are mainly distributed in microporous channels. This gradient distribution structure perfectly matches the pore structure and functional group distribution of the carrier, enabling simultaneous aerobic and anaerobic metabolic processes. The microorganisms are covalently fixed to the internal pores of the carrier, ensuring a strong bond and preventing detachment. The spatial structure of the gradient-functionalized microbial-carrier complex matches the spatiotemporal phase separation mode of plasma interaction, allowing intermediate products generated in the plasma interaction phase to rapidly diffuse through macropores into the internal pores, providing substrates for the microorganisms.

[0053] The dielectric barrier discharge plasma reactor unit is the core equipment for achieving the spatiotemporal phase separation symbiotic relationship between low-temperature plasma and microorganisms. It is used to generate pulse-modulated non-equilibrium low-temperature plasma, providing high-energy active species for the activation of stable pollutants in tailings. The design of the reactor unit is perfectly matched with the structural characteristics of the gradient functionalized microorganism-carrier complex and the process requirements of spatiotemporal phase separation treatment, enabling precise synchronization of plasma discharge and material transport.

[0054] The dielectric barrier discharge plasma reactor adopts a vertical flat-plate structure, mainly composed of a reactor chamber, upper and lower electrode assemblies, a quartz dielectric plate, a pulse power supply system, and gas interface. The reactor chamber is welded from 304 stainless steel, with a wall thickness of 5-8 mm, and can withstand a working pressure of 0.1-0.2 MPa. 304 stainless steel is resistant to acid and alkali corrosion, resisting the erosion of acidic gases generated during the process. A flange sealing cover is installed at the top of the chamber, and a silicone rubber sealing ring is used to seal the flange cover and the chamber to ensure the reactor's airtightness. A working gas inlet is located at the center of the flange sealing cover, connected to a gas mixer via a pipe. Below the working gas inlet is a perforated gas distributor plate with a perforation diameter of 1-2 mm and a perforation spacing of 5-10 mm, ensuring uniform distribution of the working gas within the plasma interaction zone. An exhaust port is located at the bottom of the chamber, connected to an exhaust gas treatment unit via a pipe.

[0055] The upper and lower electrode assemblies are arranged parallel to each other inside the reactor chamber. The upper electrode is fixed to the lower surface of the flange sealing cover, and the lower electrode is fixed to a PTFE insulating support at the bottom of the chamber. Both electrodes are made of 304 stainless steel with polished surfaces, achieving a roughness lower than Ra0.8μm to reduce partial discharge and improve discharge uniformity. The upper and lower electrodes are identical in size, with a length of 300-500mm and a width of 200-300mm. Both electrodes are covered with a quartz dielectric plate, the size of which perfectly matches the electrode dimensions, with a thickness of 2-5mm. The quartz dielectric plate is fixed to the electrode surface using high-temperature resistant silicone rubber strips to prevent displacement caused by discharge vibration. The quartz dielectric plate features high dielectric constant, good insulation, and high-temperature resistance, effectively blocking arc discharge and maintaining a stable dielectric barrier discharge state. The spacing between the upper and lower electrodes can be adjusted via the lifting mechanism of the insulating support, with an adjustment range of 10-50mm to accommodate material layers of different thicknesses.

[0056] The pulse power supply system employs a bipolar pulsed DC power supply with an output voltage range of 10-30kV, a pulse frequency range of 1-100Hz, and a duty cycle range of 1%-50%. The bipolar pulse prevents the accumulation of space charge on the quartz dielectric plate surface, preventing plate breakdown. Simultaneously, it rapidly dissipates plasma active species during pulse intervals, preventing their diffusion into non-plasma interaction zones and potential damage to microorganisms. The pulse power supply system incorporates overcurrent, overvoltage, and short-circuit protection modules, automatically cutting off power in case of abnormal discharge to protect the equipment. The system also features a synchronous trigger interface connected to the servo motor controller of the rotatable material tray via a signal line. The rotational position signal output by the servo motor controller achieves hard synchronization with the pulse power supply's trigger signal, ensuring the discharge cycle of the pulse power supply perfectly matches the residence time of the material tank in the plasma interaction zone. The pulse power supply outputs its first pulse when the front end of the material tank enters the area directly opposite the upper and lower electrodes; it stops outputting pulses when the rear end of the material tank leaves this area.

[0057] The reactor chamber is divided into a plasma interaction zone and a non-plasma interaction zone. The area directly opposite the upper and lower electrodes is the plasma interaction zone, the area of ​​which is matched to the area of ​​a single material tank to ensure that the mixture within the tank is uniformly covered by plasma. The area outside the upper and lower electrodes is the non-plasma interaction zone, the volume of which is 3-5 times that of the plasma interaction zone. This volume ratio is matched to the ratio of plasma interaction time to microbial metabolism time, ensuring that microorganisms have sufficient time to complete the mineralization process of pollutants. A gas collection port is installed at the top of the non-plasma interaction zone, connected to a gas collection hood via a pipe, to collect gases produced by microbial metabolism.

[0058] A quartz observation window, measuring 100mm × 100mm, is installed on the side wall of the reactor chamber to observe the plasma discharge state and material movement inside the reactor. The quartz observation window is sealed to the side wall of the chamber using a flange to ensure the reactor's airtightness.

[0059] The material conveying and spatiotemporal phase separation unit is the core actuator for achieving the synergistic coexistence of low-temperature plasma and microorganisms through spatiotemporal phase separation. It is responsible for periodically and alternately conveying the mixed materials to the plasma interaction zone and non-plasma interaction zone, precisely cooperating with the dielectric barrier discharge plasma reactor unit to construct a processing mode coupled with alternating time pulses and dynamic spatial switching. The design of the material conveying and spatiotemporal phase separation unit is perfectly matched with the plasma discharge parameters and microbial metabolic kinetics, ensuring that each batch of materials undergoes the same processing cycle and reaction conditions.

[0060] The material conveying and spatiotemporal phase separation unit mainly consists of a rotatable material tray, a drive control system, and an infeed / outfeed system. The rotatable material tray is positioned between the upper and lower electrodes inside the dielectric barrier discharge plasma reactor. The tray body is made of 304 stainless steel, with a diameter of 400-600 mm and a thickness of 10-15 mm. Multiple detachable material troughs, 4-8 in number, are evenly distributed along the circumference of the tray body. Each material trough has the same length and width as the plasma interaction zone, and a depth of 10-25 mm, matching the preset material layer thickness. The material troughs adopt a drawer-type structure, fixed to the tray body by slots, and can be individually disassembled for cleaning, replacement, or material sampling. The bottom of each material trough has multiple vent holes with a diameter of 1-2 mm and a spacing of 5-10 mm, which promotes mass transfer of reactant gases within the material layer and improves processing uniformity.

[0061] The drive control system mainly consists of a servo motor, a synchronous belt drive mechanism, and a position detection device. The servo motor is fixed to the outside of the bottom of the reactor chamber, and its output shaft extends into the reactor chamber through a sealing assembly. The synchronous belt drive mechanism connects the servo motor's output shaft to the central shaft of the rotatable material tray, with a transmission ratio of 1:1, ensuring that the servo motor's speed is completely synchronized with the tray's speed. The position detection device uses a photoelectric proximity switch. The proximity switch's detection head is fixed to the side wall of the reactor chamber, and the detection target is a sensing plate fixed to the edge of the tray body. The number of sensing plates is the same as the number of material troughs, with each sensing plate corresponding to the center position of a material trough. When a sensing plate passes through the detection area of ​​the proximity switch, the proximity switch outputs a trigger signal to the servo motor controller and the pulse power supply system.

[0062] The servo motor controller can precisely adjust the rotation speed of the tray, with an adjustment range of 0.1-1 r / min. After receiving the trigger signal from the position detection device, the servo motor controller can calibrate the rotation position of the tray in real time, eliminating accumulated errors and ensuring the alignment accuracy between the material tank and the plasma interaction zone. The pulse power supply system is hard-synchronized with the servo motor controller. When the front induction plate of the corresponding material tank triggers the proximity switch, the pulse power supply system starts discharging; when the rear induction plate of the material tank triggers the proximity switch, the pulse power supply system stops discharging. In this way, it is ensured that the plasma power supply will only output pulses during the time period corresponding to the material tank within the plasma interaction zone, achieving precise synchronization between plasma discharge and material position.

[0063] The feeding and discharging system includes a top feed hopper, a feed control valve, a bottom discharge hopper, and a scraper discharge mechanism. The top feed hopper is located on the top flange sealing cover of the reactor chamber, above the non-plasma interaction zone. The feed control valve is installed at the outlet of the top feed hopper and controls the feed rate and quantity. When the empty material trough rotates to below the top feed hopper, the feed control valve automatically opens, uniformly adding the mixed material into the trough. After feeding is complete, the feed control valve automatically closes. The scraper discharge mechanism is located at the bottom of the reactor chamber, between the non-plasma interaction zone and the feed position. The scraper height of the scraper discharge mechanism is adjustable, maintaining a gap of 0.5-1mm with the bottom of the material trough. When the processed material trough rotates to the scraper discharge mechanism position, the scraper scrapes the processed material in the trough into the bottom discharge hopper and discharges it outside the reactor.

[0064] The rotation speed of the rotatable material tray is adjusted according to preset plasma treatment time and microbial treatment time. One complete rotation of the tray constitutes one treatment cycle, with the time the material trough spends in the plasma treatment zone being the plasma treatment time, and the time spent in the non-plasma treatment zone being the microbial treatment time. By adjusting the tray's rotation speed and the number of material troughs, the ratio of plasma treatment time to microbial treatment time can be independently adjusted to meet the needs of tailings treatment of different types and contamination levels.

[0065] A mechanical seal assembly is used to seal the reactor chamber and the central axis of the rotatable material tray. The mechanical seal assembly is made of acid and alkali resistant silicon carbide, which ensures the airtightness of the reactor and prevents gas leakage. The edge of the tray body is provided with an annular retaining edge with a height of 20-30mm to prevent material from spilling from the edge of the tray during rotation.

[0066] The gas circulation and closed-loop control unit is the core unit for achieving the closed-loop symbiotic relationship between low-temperature plasma and microbial matter. It is responsible for collecting gases produced by microbial metabolism, purifying them, mixing them with air in a specific ratio, and then feeding them into the plasma reactor as working gas. Simultaneously, it dynamically adjusts plasma parameters and gas mixing ratios based on changes in gas phase composition, achieving bidirectional material circulation and synergistic effects. The design of the gas circulation and closed-loop control unit is perfectly matched to the plasma discharge characteristics and the composition of microbial metabolites, ensuring that the reused gas will not negatively impact the stability of the plasma discharge or the metabolic activity of the microorganisms.

[0067] The gas circulation and closed-loop control unit mainly consists of a gas collection hood, a two-stage gas purification device, a static gas mixer, an oil-free diaphragm gas pump, an online gas phase component detection device, a closed-loop controller, and an electric flow regulating valve. The gas circulation path is as follows: microbial metabolic gases generated in the non-plasma interaction zone are collected by the gas collection hood and then sent to the two-stage gas purification device to remove solid impurities. The purified gas is then sent to the static gas mixer to mix with compressed air. The mixed gas is pressurized by the oil-free diaphragm gas pump and then sent to the working gas inlet of the plasma reactor. The exhaust gas after the plasma reaction is sent to the exhaust gas treatment unit for treatment before being discharged.

[0068] The gas collection hood features an arc-shaped structure, covering the entire upper space of the non-plasma interaction zone. The lower edge of the gas collection hood is 50-100mm from the upper surface of the rotatable material tray. The arc-shaped structure improves gas collection efficiency and prevents gas diffusion into the plasma interaction zone. A gas outlet is located at the top of the gas collection hood, connected to a two-stage gas purification device via PTFE piping. The PTFE piping is resistant to acid and alkali corrosion, resisting the erosion of hydrogen sulfide and acidic gases.

[0069] The two-stage gas purification system employs a series structure. The first stage is a bag filter, and the second stage is a hydrophobic molecular sieve adsorption column. The bag filter removes tailings dust and carrier particles entrained in the gas. The hydrophobic molecular sieve adsorption column removes water vapor and trace organic impurities from the gas. The hydrophobic molecular sieve has extremely weak adsorption capacity for hydrogen sulfide and carbon dioxide, ensuring the recovery rate of the target reusable components. Differential pressure sensors are installed at the inlet and outlet of both stages of the gas purification system to monitor for blockages.

[0070] The static gas mixer adopts the SK type static mixer, with 3-5 sets of spiral blades inside, and the mixing uniformity deviation is less than 5%. The two air inlets of the static gas mixer are connected to the outlet of the two-stage gas purification device and the compressed air source, respectively. Both air inlets are equipped with electric flow regulating valves, and the adjustment accuracy of the electric flow regulating valves is ±1%.

[0071] An oil-free diaphragm gas pump is installed between the outlet of the static gas mixer and the inlet of the plasma reactor, with a gas flow rate adjustable from 10 to 100 L / min. The oil-free diaphragm gas pump does not introduce oil impurities, thus preventing oil contamination of the plasma discharge environment and avoiding impact on microbial metabolic activity.

[0072] The online gas phase component detection device has two detection points. The first detection point is located in the outlet pipeline of the two-stage gas purification device, used to detect the concentrations of carbon dioxide and hydrogen sulfide in the purified microbial metabolic gas. The second detection point is located in the outlet pipeline of the static gas mixer, used to detect the concentration of oxygen in the mixed gas. The detection accuracy of the online gas phase component detection device is ±2%, and the response time is less than 30 seconds.

[0073] The closed-loop controller is electrically connected to the online gas phase component detection device, the electric flow regulating valve, and the pulse power supply system. The control logic of the closed-loop controller is as follows: when the hydrogen sulfide concentration is higher than a set threshold, the discharge power of the pulse power supply is increased to increase the generation of sulfur free radicals and enhance the sulfide oxidation reaction; when the carbon dioxide concentration is lower than a set threshold, the proportion of compressed air flow is increased to increase the generation of nitrogen oxides in the plasma reaction and supplement the nitrogen source required for microbial metabolism; when the oxygen concentration is higher than a set threshold, the proportion of compressed air flow is decreased to prevent excessive oxygen from entering the non-plasma interaction zone and disrupting the anaerobic microenvironment. The closed-loop controller can adjust the gas mixing ratio and plasma parameters in real time to ensure the dynamic balance between the plasma reaction and microbial metabolism.

[0074] An emergency vent valve is installed in the gas circulation pipeline, and the valve is electrically connected to the closed-loop controller. When the hydrogen sulfide concentration exceeds the safety threshold, the closed-loop controller automatically opens the emergency vent valve, releasing the gas into the exhaust gas treatment unit, and simultaneously shuts down the oil-free diaphragm gas pump to ensure safe system operation. Tailings pretreatment and material mixing are preliminary steps to ensure the uniformity and stability of the low-temperature plasma-microorganism synergistic treatment effect. By removing harmful impurities from the tailings, adjusting the physical properties of the tailings, and achieving uniform mixing of the tailings with the gradient functionalized microorganism-carrier complex, qualified reaction materials are provided for subsequent spatiotemporal phase separation treatment. The parameter design of the tailings pretreatment and material mixing process is perfectly matched with the plasma discharge characteristics and microbial metabolic requirements, which can avoid the interference of impurities on the treatment process and ensure the mass transfer efficiency of the reaction system.

[0075] The specific implementation steps are as follows: S1. Tailings Crushing, Screening, and Multi-stage Impurity Removal. The tailings to be processed are fed into a jaw crusher for primary crushing, ensuring the maximum particle size of the crushed tailings does not exceed 5mm. The crushed tailings are then fed into a vibrating screen with a 5mm mesh size to remove large pieces of gravel and impurities larger than 5mm. The screened tailings are then sent to a manual sorting table to remove large organic impurities such as waste plastics and waste wood. These large organic impurities, under the influence of plasma, will produce toxic and harmful gases and simultaneously encapsulate the tailings particles, hindering contact between pollutants and active species and microorganisms. The sorted tailings are then fed into a drum magnetic separator with a magnetic field strength controlled at 1000-1500Gs. This magnetic field strength can remove most of the free ferromagnetic minerals in the tailings without adsorbing useful iron-containing components. Ferromagnetic impurities distort the plasma electric field, inducing localized tip discharges, disrupting discharge uniformity, and simultaneously abrading the carrier structure and releasing metal ions that inhibit microbial activity.

[0076] S2. Tailings Moisture Content Adjustment. Spread the cleaned tailings evenly in a well-ventilated and dry area, allowing them to air dry naturally for 24-48 hours, or send them to a rotary dryer for low-temperature drying. The drying temperature should not exceed 60℃, as temperatures exceeding 60℃ will cause the microorganisms in the subsequently added gradient functionalized microorganism-carrier complex to become inactive upon contact with the high-temperature tailings. The tailings moisture content is tested using a drying method, with samples taken every 2 hours. When the tailings moisture content is below 10%, deionized water is evenly sprayed onto the tailings using atomized spraying, with the atomized particle size controlled at 50-100μm to avoid localized overwetting and the formation of mud clumps, adjusting the tailings moisture content to 10%-15%. Excessive tailings moisture content will cause plasma energy to be consumed by water evaporation, reducing the efficiency of active species generation; excessively low tailings moisture content will inhibit the metabolic activity of microorganisms and block the extracellular electron transfer process.

[0077] S3. Uniform Mixing of Materials. The tailings with adjusted moisture content and the gradient functionalized microorganism-carrier complex are added to a horizontal ribbon mixer at a mass ratio of (5-10):1. The inner wall of the horizontal ribbon mixer is lined with a polyurethane wear-resistant lining to reduce wear from the tailings and prevent the introduction of metallic impurities. The speed of the horizontal ribbon mixer is controlled at 30-50 r / min, and the mixing time is 10-15 min. After mixing, three parallel samples are taken from the feed end, middle, and discharge end of the mixer. The mass fraction of the gradient functionalized microorganism-carrier complex in each sample is measured, and the relative standard deviation is calculated. A relative standard deviation of less than 5% indicates uniform mixing. Too low a proportion of the gradient functionalized microorganism-carrier complex will result in insufficient catalytic active sites and microbial quantity, reducing treatment efficiency; too high a proportion will increase treatment costs and reduce the porosity of the material layer, affecting gas mass transfer efficiency.

[0078] The mixed material should be promptly transferred to the material trough of the rotating material tray, and the placement time should not exceed 2 hours. After 2 hours, the activity of microorganisms in the gradient functionalized microorganism-carrier complex will decrease due to nutrient depletion and moisture evaporation. The bulk density of the mixture should be controlled between 1.2-1.5 g / cm³ by adjusting the particle size distribution of the tailings and the addition ratio of the gradient functionalized microorganism-carrier complex. 3 With a porosity of 40%-50%, it ensures that the reactant gas can diffuse evenly within the material layer.

[0079] The spatiotemporal phase-separated symbiotic synergistic treatment process is the core technological step of this invention. By periodically and alternately transporting the mixed materials to the plasma-enhanced and non-plasma-enhanced zones, the spatiotemporal separation and synergistic coupling of plasma activation and microbial mineralization are achieved. This process fully utilizes the spatial isolation structure of the gradient-functionalized microbial-carrier complex and the closed-loop mechanism of gas circulation to solve the problems of plasma damage to microorganisms and mutual inhibition of the two reactions in existing synergistic technologies, thereby achieving the oxidation of sulfides and the stabilization of heavy metals in tailings.

[0080] The specific implementation steps are as follows: S1. System Start-up and Parameter Preset. Evenly spread the mixed material into the material trough of the rotatable material tray, controlling the thickness to 5-20mm. Avoid material clumping during spreading to ensure a smooth surface. The spreading thickness should match the effective penetration depth of the plasma to ensure uniform plasma action on the surface of the tailings particles. Start the servo motor and adjust the tray rotation speed to the preset value, ensuring the material trough's residence time in the plasma zone is 1-5 minutes and in the non-plasma zone is 5-20 minutes. Start the pulse power supply system, preset the initial pulse voltage to 15-25kV, pulse frequency to 10-50Hz, and duty cycle to 5%-20%. Start the gas circulation unit, preset the initial compressed air flow rate to 20-60L / min and the gas circulation flow rate to 10-30L / min. Run the system unloaded for 5 minutes to check if the plasma discharge is uniform and arc-free, if the gas flow rate is stable at the preset value, if the trigger signal of the position detection device is normal, and if the servo motor's rotation position is accurate. After confirming no abnormalities, begin formal processing.

[0081] S2, Plasma-Action Phase. The mixed material rotates with the tray and enters the plasma-action zone directly opposite the upper and lower electrodes. The pulse power system automatically starts discharging based on the trigger signal from the position detection device. High-energy electrons, reactive oxygen species, and reactive nitrogen species are generated in the plasma field. High-energy electrons bombard the tailings surface, breaking the chemical bonds between stable heavy metals and silicates and sulfides, converting the difficult-to-leach bound heavy metals into ionic reactive heavy metals that are easily mineralized by microorganisms. Reactive oxygen species oxidize metal sulfides in the tailings to generate soluble metal sulfates, providing a sulfur source for subsequent microbial metabolism. The ferric oxide catalyst on the outer surface of the carrier and the inner wall of the macropores catalyzes the generation of reactive oxygen and nitrogen species, improving the activation efficiency of pollutants. The carbon dioxide and nitrogen oxides generated by the plasma reaction diffuse with the airflow to the non-plasma-action zone, providing carbon and nitrogen sources for microbial metabolism. The effective action distance of the plasma-active species is less than 1 μm, and it can only act on the surface of tailings particles and the outer surface of the carrier. It cannot penetrate the macropores of the carrier to enter the internal mesopores and micropores, so the microorganisms are not directly damaged by the plasma.

[0082] S3, Microbial Action Phase. The mixture rotates with the tray, leaving the plasma action zone and entering the non-plasma action zone. Aerobic sulfur-oxidizing and iron-oxidizing bacteria in the mesoporous channels inside the carrier utilize the oxygen and intermediate products generated by the plasma reaction for metabolic activities. Sulfur-oxidizing bacteria completely oxidize incompletely oxidized sulfides and sulfites to sulfates. Iron-oxidizing bacteria oxidize ferrous ions to ferric ions, which then co-precipitate hydroxides with active heavy metal ions. Anaerobic sulfate-reducing bacteria in the microporous channels inside the carrier utilize hydrogen and small-molecule organic acids generated from the plasma decomposition of water and trace organic matter in tailings as electron donors to reduce sulfates to sulfide ions. Sulfide ions react with active heavy metal ions to form stable metal sulfide precipitates. Heavy metal-tolerant bacteria convert the remaining active heavy metal ions into stable carbonate and phosphate precipitates through extracellular adsorption, intracellular accumulation, and biomineralization. The overall microbial mineralization reaction is as follows:

[0083] In the formula: It is an active divalent heavy metal ion; It is a sulfate ion; It is a carbonate ion; Phosphate ions These are the stoichiometric coefficients for the corresponding reactions; It is a precipitate of metal sulfides; It is a precipitate of metal carbonates; It is a metal phosphate precipitate.

[0084] S4. Gas Circulation and Closed-Loop Control. Carbon dioxide and hydrogen sulfide produced by microbial metabolism in the non-plasma interaction zone are collected by a gas collection hood. After dust and impurities are removed by a two-stage gas purification device, the gas is sent to a static gas mixer and mixed with compressed air in a preset ratio. The mixed gas is pressurized by an oil-free diaphragm gas pump and then sent to the plasma reactor as the working gas. Hydrogen sulfide in the mixed gas decomposes in the plasma field to generate highly reactive sulfur free radicals, further enhancing the oxidation reaction of metal sulfides. The basic reactions of hydrogen sulfide plasma decomposition are as follows:

[0085] In the formula: Hydrogen sulfide produced by microbial metabolism; It is a hydrogen free radical; It is a thiol free radical. The thiol free radical can further react to generate sulfur free radicals and hydrogen gas. Sulfur free radicals have strong oxidizing properties and can directly oxidize metal sulfides.

[0086] The online gas phase component detection device monitors the changes in the composition of the purified metabolic gas and mixed gas in real time and transmits the detection signals to the closed-loop controller. The closed-loop controller has preset thresholds for hydrogen sulfide concentration of 50-200 ppm, carbon dioxide concentration of 1%-5%, and oxygen concentration of 15%-21%. According to the preset control logic, the closed-loop controller adjusts the opening degree of the electric flow regulating valve and the operating parameters of the pulse power supply system in real time to ensure the dynamic balance between plasma reaction and microbial metabolism.

[0087] S5. Cyclic Processing and Endpoint Determination. After the mixed material completes one processing cycle as the tray rotates, it re-enters the plasma treatment zone and repeats the processing steps S2 to S4. Samples are taken from different material tanks for testing every 10 processing cycles. One parallel sample is taken from the upper, middle, and lower layers of each material tank. The leaching concentration of heavy metals is determined according to GB5086.2-1997 "Solid Waste Leaching Toxicity Leaching Method - Horizontal Oscillation Method," and the sulfide content is determined according to the iodometric method. Processing is stopped when the leaching concentration of heavy metals and the sulfide content of all samples meet the relevant national standards.

[0088] During the process, the plasma discharge status and material movement are observed in real time through a quartz observation window. If local arc discharge occurs, the pulse voltage is immediately reduced until the arc disappears; if material spillage occurs, the servo motor is stopped, the spilled material is cleaned up, and operation continues; if gas leakage occurs, the gas pump and inlet valve are immediately shut off, the sealing points are checked and repaired, and operation continues.

[0089] The post-treatment material separation and carrier regeneration process is a key step in achieving the low-cost industrial application of this invention. The treated tailings sand is separated from the gradient functionalized microorganism-carrier complex using physical separation methods. The separated carrier is then cleaned and activated to restore its catalytic and microbial metabolic activity, enabling the carrier to be recycled and reused, thus reducing material consumption and operating costs. The parameters of the post-treatment material separation and carrier regeneration process are designed to match the structural characteristics of the gradient functionalized microorganism-carrier complex, avoiding irreversible damage to the carrier structure and microbial activity during separation and regeneration.

[0090] The specific implementation steps are as follows: S1. Collection and Pretreatment of Post-Processed Materials. The post-processed materials discharged from the reactor are collected in a sealed container to prevent spillage and secondary contamination. The collected materials are then fed into a horizontal disperser, with the disperser speed controlled at 100-150 r / min, and a processing time of 3-5 min. A speed range of 100-150 r / min effectively disperses agglomerates in the material without damaging the porous structure of the gradient functionalized microorganism-carrier complex and the surface-loaded ferric oxide catalyst. The dispersed material particles are uniformly dispersed, creating conditions for subsequent screening and separation.

[0091] S2. Vibrating Screening and Grading Separation. The dispersed material is fed into a double-layer linear vibrating screen for grading and separation. The double-layer linear vibrating screen adopts the principle of grading and screening, which can achieve continuous separation of materials with different particle sizes. The aperture of the upper screen is 0.3mm, and the aperture of the lower screen is 0.15mm. The vibration frequency of the vibrating screen is controlled at 1500-2000 times / min, and the amplitude is controlled at 2-3mm. The particle size range of the gradient functionalized microorganism-carrier complex is 0.18-0.25mm, which is consistent with the particle size of the 60-80 mesh porous biochar substrate prepared in Section 2.1, so it will be trapped between the upper and lower screens; most of the treated tailings particles are smaller than 0.15mm and will be discharged through the lower screen; a small amount of unbroken impurities with a particle size greater than 0.3mm will be trapped by the upper screen, collected and processed uniformly. The screening and separation efficiency can reach over 95%, and the loss rate of the carrier during the screening process is controlled below 5%, ensuring effective separation of the carrier and tailings and reducing carrier loss.

[0092] S3. Aseptic Cleaning of the Carrier. The gradient functionalized microorganism-carrier complex trapped between two layers of sieves is collected and placed in a stirred cleaning tank. Sterile physiological saline at 25-30℃ is added, with a solid-liquid ratio controlled at 1:10. The stirring speed is controlled at 80-100 rpm, and the cleaning time is 5-10 minutes. The temperature of 25-30℃ is consistent with the optimal growth temperature of the complex functional microbial community, avoiding the impact of temperature changes on microbial activity. After cleaning, allow to settle for 10 minutes, discard the supernatant, and repeat the cleaning 2-3 times until the cleaning solution is clear and free of obvious suspended matter. Sterile physiological saline does not introduce harmful impurities or significantly affect the microbial activity inside the carrier, and effectively removes tailings particles and microbial metabolic byproducts attached to the carrier surface.

[0093] S4. Activation and Cultivation of the Carrier. The cleaned gradient functionalized microorganism-carrier complex was transferred to the bioreactor, and modified 9K liquid medium was added, with a solid-liquid ratio controlled at 1:15. The modified 9K liquid medium has the same composition as the medium used in the domestication process of the composite functional microbial community in Section 2.4, which can rapidly restore the metabolic activity of the microorganisms. The bioreactor temperature was controlled at 30℃, the stirring speed at 100-120 r / min, and the aeration rate at 0.5-1.0 vvm. The aeration rate of 0.5-1.0 vvm ensures the growth requirements of aerobic microorganisms without generating excessive shear force that could damage the carrier structure and microbial cells. The activation and cultivation time was 24-48 h, during which samples were taken every 12 h to detect the dehydrogenase activity of the microorganisms. The microbial dehydrogenase activity was detected using the TTC colorimetric method. Activation and cultivation were stopped when the microbial dehydrogenase activity recovered to more than 90% of the initial carrier activity. During the activation culture process, the culture medium provides sufficient nutrients for the microorganisms, restores their metabolic activity, and does not damage the ferric oxide catalyst on the carrier surface.

[0094] S5. Recycling and Disposal of the Carrier. The activated, gradient-functionalized microorganism-carrier composite can be returned to the material mixing process and reused after mixing with pretreated tailings. The carrier can be recycled 10-15 times, significantly reducing material costs in the treatment process. When the microbial dehydrogenase activity of the carrier is less than 60% of its initial activity, or the ferric oxide catalyst loading is less than 50% of its initial loading, the carrier loses its recycling value and must be disposed of. The waste carrier is rendered harmless by high-temperature calcination at 500-600℃ for 2-3 hours. The temperature of 500-600℃ completely decomposes the microorganisms and organic pollutants in the carrier while retaining the basic structure of biochar. The calcined product can be used as a raw material for building materials or safely landfilled.

[0095] This invention constructs a triple-synergistic tailings harmless treatment system based on the spatial isolation effect of gradient functionalized carriers, the spatiotemporal phase separation synergistic effect of plasma and microorganisms, and the material closed-loop symbiotic effect of gas circulation. This system addresses the core problems of existing plasma-microorganism synergistic technologies, such as plasma damaging microorganisms, mutual inhibition of the two reactions, and low material utilization. The working principle and synergistic mechanism of this invention permeate the entire process of carrier preparation, reactor design, and process operation. There are close internal connections between each technical link, jointly achieving the complete oxidation of sulfides and the long-term stabilization of heavy metals in tailings.

[0096] The spatial isolation principle of the gradient-functionalized microbial-carrier complex is the foundation for the plasma-microbial symbiosis of this invention. The hierarchical pore structure of the porous biochar substrate provides the physical framework for spatial isolation. Macropores are used for gas mass transfer and catalyst loading, while mesopores and micropores are used for microbial immobilization. Surface-internal gradient functional group modification constructs an interface with hydrophobic outer layer and hydrophilic inner layer. The hydrophobic long-chain alkyl groups on the outer surface prevent water-soluble iron salt precursors and microorganisms from entering the internal pores, while providing loading sites for the iron-based oxide catalyst. The hydrophilic carboxyl functional groups in the internal pores provide covalent binding sites for microorganisms. The iron-based oxide catalyst is only loaded on the outer surface and the inner wall of the macropores, while the composite functional microbial community is only immobilized in the internal mesopores and micropores, forming a spatially separated structure between the catalyst and microorganisms. The effective interaction distance of the plasma-active species is less than 1 μm, and it can only act on the surface of tailings particles and the outer surface of the carrier. It cannot penetrate the macropores of the carrier to enter the internal mesopores and micropores, so the microorganisms are not directly damaged by the plasma. The spatial isolation structure of the carrier fundamentally solves the problem of microbial inactivation caused by direct contact between plasma and microorganisms in traditional collaborative technologies.

[0097] The spatiotemporal phase separation synergy mechanism of plasma and microorganisms is the core of this invention for achieving high-efficiency treatment. Plasma reactions and microbial mineralization reactions have different kinetic characteristics and environmental requirements: plasma reactions are fast, breaking the chemical bonds of stable pollutants within minutes, but the reaction products are unstable and prone to reverse reactions; microbial mineralization reactions are slow, requiring several minutes to tens of minutes to convert active products into stable mineral phases, but the reaction products are stable and can achieve long-term fixation of heavy metals. This invention divides the reactor's internal space into plasma-interactive and non-plasma-interactive zones using a rotatable material tray, allowing the mixed materials to periodically alternate between the two zones, achieving temporal separation of plasma activation and microbial mineralization; simultaneously, plasma activation and microbial mineralization reactions occur in different spaces at the same time, achieving spatial parallelism of the two reactions. Hard synchronization control of the pulsed power supply system and servo motor controller ensures that only materials within the plasma-interactive zone are affected by plasma, preventing the diffusion of active species to the non-plasma-interactive zone. The spatiotemporal phase separation mode allows both plasma reactions and microbial mineralization reactions to proceed under their respective optimal environmental conditions, eliminating mutual inhibition between the two reactions, while simultaneously improving treatment efficiency through temporal alternation and spatial parallelism.

[0098] The closed-loop symbiotic mechanism of gas circulation is key to achieving synergistic effects and reducing costs in this invention. Carbon dioxide, nitrogen oxides, and sulfates generated during the plasma reaction serve as carbon, nitrogen, and sulfur sources for microbial metabolism, providing nutrients for microbial growth. Carbon dioxide and hydrogen sulfide generated during microbial metabolism can be recycled into the plasma reactor as working gases, enhancing the plasma reaction. Hydrogen sulfide in the mixed gas decomposes in the plasma field to generate highly reactive sulfur radicals. These sulfur radicals have higher oxidizing activity than oxygen and hydroxyl radicals, directly oxidizing metal sulfides in tailings and improving sulfide oxidation efficiency. The closed-loop controller dynamically adjusts the gas mixing ratio and plasma parameters based on real-time changes in gas phase composition, ensuring a dynamic balance between the plasma reaction and microbial metabolism, forming a bidirectional symbiotic system of material circulation. This closed-loop mechanism not only improves material utilization and reduces operating costs but also further strengthens the synergistic effect between the two technologies.

[0099] The triple synergistic effect of this invention promotes and supports each other: the spatial isolation effect provides the structural basis for spatiotemporal phase separation synergy and material closed-loop symbiosis; the spatiotemporal phase separation synergy provides the operating conditions for the spatial isolation effect to take effect, while providing reaction substrates for material closed-loop symbiosis; the material closed-loop symbiosis further enhances the treatment effect of spatiotemporal phase separation synergy, while reducing operating costs. The organic combination of the triple synergistic effect makes the treatment efficiency of this invention significantly higher than that of single plasma technology or single microbial technology, while solving the core pain points of existing synergistic technologies.

[0100] For the specific operational methods of microbial dehydrogenase activity detection, heavy metal leaching toxicity detection, and sulfide content detection, those skilled in the art can perform them in accordance with relevant national standards and industry specifications. These detection methods are well-known technologies in the field and will not be elaborated further here. For the specific circuit design and programming of pulse power supply control, servo motor drive, and online detection of gaseous components, those skilled in the art can implement them using conventional industrial control technologies. These control technologies are well-known technologies in the field and will not be elaborated further here.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for harmless treatment of tailings using a low-temperature plasma-microorganism synergistic approach, characterized in that, Includes the following steps: S1. Prepare a gradient functionalized microbial-carrier composite, wherein the gradient functionalized microbial-carrier composite uses porous biochar as a substrate, with ferric oxide catalyst loaded on the outer surface and macropores, and composite functional bacterial groups fixed in the internal mesopores and micropores. S2. The tailings to be treated are crushed, screened, impurities removed and moisture content adjusted. The pretreated tailings are then uniformly mixed with the gradient functionalized microorganism-carrier complex at a mass ratio of (5-10):1 to obtain a mixture. S3. The mixture is fed into a vertical flat plate dielectric barrier discharge plasma reactor. The mixture is periodically alternately introduced into the plasma interaction zone and the non-plasma interaction zone through a rotatable material tray for spatiotemporal phase separation symbiotic synergistic treatment. The active species generated in the plasma interaction zone activate the stable pollutants in the tailings, while the composite functional bacteria in the non-plasma interaction zone transform the active pollutants into stable mineral phases. S4. Collect the microbial metabolic gas generated in the non-plasma interaction zone, purify it and mix it with compressed air in a certain proportion, and reuse it in the plasma reactor as working gas. Dynamically adjust the gas mixing ratio and plasma operating parameters according to the changes in gas phase composition to achieve bidirectional material closed-loop circulation and synergistic effect. S5. After treatment, the treated tailings are separated from the gradient functionalized microorganism-carrier complex. The gradient functionalized microorganism-carrier complex is then cleaned, activated, and cultured for reuse.

2. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 1, characterized in that, The preparation of the gradient functionalized microbial-carrier complex in step S1 includes the following steps: preparing a porous biochar substrate using agricultural waste as raw material, wherein the porous biochar substrate has macropores with a pore size greater than 50 nm, mesopores with a pore size of 2-50 nm, and micropores with a pore size less than 2 nm. Surface-internal gradient functional group modification was performed on porous biochar substrates to construct a gradient functional group distribution of hydrophobic macropores and hydrophilic mesopores and micropores on the outer surface and macropores. Selective gradient loading of iron-based oxide catalysts was carried out on the modified porous biochar, so that ferric oxide nanoparticles were distributed only on the outer surface and the inner wall of the macropores. A gradient fixation of composite functional microbial communities was carried out on porous biochar loaded with catalyst, so that aerobic microorganisms were distributed in mesoporous channels and anaerobic microorganisms were distributed in microporous channels.

3. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 2, characterized in that, The specific steps of the surface-internal gradient functional group modification are as follows: the porous biochar substrate is placed in a vacuum impregnation device, the vacuum is drawn to an absolute pressure of less than 1 kPa, an octadecyltrichlorosilane-hexane solution with a concentration of 5%-10% is injected, and the reaction is carried out at 25-40℃ for 2-4 hours to complete the hydrophobic modification of the outer surface and macropores. The hydrophobically modified porous biochar was immersed in a 10%-20% polyethylene glycol 2000 aqueous solution and ultrasonically impregnated at 25-35℃ for 1-2 hours to achieve mesoporous and microporous channel template sealing. After the template is sealed, the porous biochar is added to an aqueous solution of acrylic acid with a concentration of 5%-15% and an ammonium persulfate initiator. The pH is adjusted to 3-4, nitrogen gas is introduced to remove oxygen, and the reaction is carried out at 50-70℃ for 3-6 hours to complete the hydrophilic modification of the mesoporous and microporous channels. The hydrophilically modified porous biochar was placed in a mixed solution of anhydrous ethanol and deionized water in a volume ratio of 1:1, and eluted by heating and reflux for 4-6 hours to remove polyethylene glycol 2000 template molecules, thus obtaining porous biochar modified with surface-internal gradient functional groups.

4. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 2, characterized in that, The specific steps for selective gradient loading of the iron-based oxide catalyst are as follows: prepare an aqueous solution of ferric nitrate nonahydrate with a concentration of 0.5-1.5 mol / L as a precursor, immerse the modified porous biochar in the precursor solution, and let it stand at 25-35℃ for 1-3 hours. The porous biochar after adsorbing iron ions was dried at 60-80℃ for 12-24h, transferred to a tube furnace, and heated to 300-400℃ for 2-4h at a heating rate of 3-5℃ / min under nitrogen protection at a rate of 100-150mL / min. After cooling, it was washed three times with deionized water and dried to obtain porous biochar loaded with ferric oxide catalyst. The ferric oxide nanoparticles have a particle size of 10-50 nm and a loading of 5%-15% by mass.

5. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 2, characterized in that, The specific steps for gradient fixation of the complex functional microbial community are as follows: Sulfur-oxidizing bacteria, iron-oxidizing bacteria, sulfate-reducing bacteria, and heavy metal-tolerant bacteria were isolated and screened from topsoil of heavy metal-contaminated mines, acidic mine wastewater, and leachate from tailings dumps. These bacteria were mixed in a colony count ratio of 2-3:1-2:1-2:1-2 and cultured for 30-60 generations before being expanded to a concentration of 10. 8 -10 9 CFU / mL bacterial suspension; The porous biochar loaded with catalyst was placed in a phosphate buffer solution with a pH of 7.2-7.4, and glutaraldehyde with a mass concentration of 2%-5% was added. The mixture was then activated by shaking at 25-30℃ for 1-2 hours. The activated porous biochar was added to the bacterial suspension at a solid-liquid ratio of 1:20 and cultured at 30℃ and 150 r / min for 24-48 h with shaking. Free microorganisms were removed by washing with sterile physiological saline to obtain a gradient functionalized microorganism-carrier complex.

6. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 1, characterized in that, The specific parameters for the spatiotemporal phase-separation co-occurrence processing in step S3 are as follows: The thickness of the mixed material is 5-20mm, and the rotation speed of the rotatable material tray is 0.1-1r / min, so that the residence time of the material tank in the plasma treatment zone is 1-5min, and the residence time in the non-plasma treatment zone is 5-20min. The pulse power supply system outputs a voltage of 15-25kV, a pulse frequency of 10-50Hz, and a duty cycle of 5%-20%. The pulse power supply system achieves hard synchronization with the servo motor controller and starts discharging only when the material tank is in the plasma action zone.

7. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 1, characterized in that, The specific methods for gas circulation and closed-loop control in step S4 are as follows: After being purified by a bag filter and a hydrophobic molecular sieve adsorption column, the microbial metabolic gas is sent to an SK-type static mixer to mix with compressed air. The mixed gas is then pressurized by an oil-free diaphragm gas pump and sent to the plasma reactor. The system monitors the concentrations of hydrogen sulfide and carbon dioxide in the purified metabolic gas and the oxygen concentration in the mixed gas online. The closed-loop controller adjusts the system based on the monitoring results: when the hydrogen sulfide concentration is higher than 50-200 ppm, the pulse power supply discharge power is increased; when the carbon dioxide concentration is lower than 1%-5%, the compressed air flow rate is increased; and when the oxygen concentration is higher than 15%-21%, the compressed air flow rate is decreased.

8. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 1, characterized in that, The specific steps for tailings pretreatment in step S2 are as follows: The tailings to be treated are crushed to a maximum particle size of no more than 5mm, screened to remove impurities larger than 5mm, and after manual sorting to remove organic impurities, they are sent to a drum magnetic separator with a magnetic field strength of 1000-1500Gs to remove ferromagnetic impurities. Dry or humidify the tailings after impurity removal, adjusting the moisture content to 10%-15%; The tailings with adjusted moisture content and the gradient functionalized microorganism-carrier composite were added to a horizontal ribbon mixer and mixed at 30-50 r / min for 10-15 min, with a mixing uniformity deviation of less than 5%.

9. The low-temperature plasma-microorganism synergistic tailings harmless treatment method according to claim 1, characterized in that, The specific steps for material separation and carrier regeneration in step S5 are as follows: The processed material is fed into a double-layer linear vibrating screen with an upper screen mesh size of 0.3 mm and a lower screen mesh size of 0.15 mm to separate gradient functionalized microorganism-carrier complex and processed tailings. The isolated gradient functionalized microorganism-carrier complex was washed 2-3 times with sterile physiological saline at 25-30℃, transferred to a bioreactor, and modified 9K liquid medium was added. The complex was then activated and cultured for 24-48 hours at 30℃, 100-120 r / min, and an aeration rate of 0.5-1.0 vvm.

10. A low-temperature plasma-microorganism synergistic tailings harmless treatment system, used to implement the low-temperature plasma-microorganism synergistic tailings harmless treatment method according to any one of claims 1 to 9, characterized in that, The system includes: A vertical flat-plate dielectric barrier discharge plasma reactor unit has its internal space divided into a plasma interaction zone and a non-plasma interaction zone. The plasma interaction zone is equipped with an electrode assembly arranged vertically and horizontally, and a pulse power supply system connected to the electrode assembly. The material conveying and spatiotemporal phase separation unit includes a rotatable material tray disposed between the upper and lower electrodes and a drive control system. The rotatable material tray has multiple material troughs with vent holes at the bottom. The drive control system drives the rotatable material tray to rotate, causing the material troughs to periodically alternately enter the plasma interaction zone and non-plasma interaction zone. The pulse power supply system is hard-synchronized with the drive control system and configured to initiate discharge only when the material trough is in the plasma interaction zone. The gas circulation and closed-loop control unit includes a gas collection hood disposed above the non-plasma interaction zone. The gas collection hood is sequentially connected to a gas purification device, a static gas mixer, and a gas pump, and then connected to the air inlet of the reactor unit. The closed-loop controller is electrically connected to an online gas phase component detection device disposed in the pipeline, the air inlet valve of the static gas mixer, and the pulse power supply system, and is configured to dynamically adjust the air intake ratio and discharge parameters according to the gas phase component detection results. The material separation and carrier regeneration unit is located downstream of the material outlet of the reactor unit, and includes a double-layer linear vibrating screen for separating treated tailings and gradient functionalized microorganism-carrier complex, and a carrier activation and cultivation device connected to the carrier outlet of the double-layer linear vibrating screen.

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