Method for preparing 5N zinc by recovering waste zinc through combination of microbial adsorption and electrodeposition

Abstract

The invention discloses a method for preparing 5N zinc by recovering waste zinc through combination of microbial adsorption and electrodeposition, and relates to the technical field of industrial wastewater treatment. According to the technical scheme, the method comprises the following steps: separating microbial strains from the zinc-containing industrial wastewater, and carrying out stress domestication to obtain high-selectivity adsorption bacteria so as to enrich zinc ions; microwave-assisted in-situ purification and electro-deposition coprocessing are realized through the nested reactor; the adsorption and electro-deposition process parameters are dynamically optimized by means of a multi-parameter self-adaptive regulation and control system; purifying a zinc product by adopting an electrolytic refining and zone melting coupling process; and recovering zinc resources from the microbial residues to prepare the bio-organic fertilizer. The method does not need the steps of genetic engineering strain modification and acid elution, reduces the loss of zinc ions, improves the purity of the electrodeposition raw material, stably prepares 5N-grade high-purity zinc, realizes resource utilization of microbial residues, forms a resource circulation closed loop, has both environmental protection benefits and economic benefits, and is suitable for high-valued treatment of zinc-containing industrial wastewater.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically a method for recovering waste zinc and preparing 5N zinc using a combination of microbial adsorption-electrodeposition. Background Technology

[0002] The recovery and high-value utilization of zinc resources in industrial wastewater is a current research hotspot in the fields of environmental protection and resource recycling. Existing technologies mostly employ microbial adsorption to enrich zinc ions, followed by zinc recovery through methods such as electrodeposition, but these generally suffer from loose process integration.

[0003] Specifically, the adsorbed zinc ions need to be transferred to the electrodeposition system through steps such as acid elution. This not only results in a high zinc ion loss rate, usually exceeding 15%, but also reduces the purity of the electrodeposition raw materials due to residual microbial organic matter in the eluent. This makes it difficult for the final product to meet the 5N grade high purity standard, which seriously restricts the economic efficiency and high-value application of waste zinc recycling.

[0004] In view of the above, this application is hereby submitted. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering waste zinc and preparing 5N zinc using a combination of microbial adsorption-electrodeposition, so as to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, this invention provides a method for recovering waste zinc and preparing 5N zinc using a combined microbial adsorption-electrodeposition process, comprising the following steps: S1 Constructing a zinc ion directional enrichment system, isolating and screening microbial strains from zinc-containing industrial wastewater, obtaining highly selective adsorption bacteria through stress acclimatization, and using these adsorption bacteria to adsorb and enrich zinc ions in the waste zinc solution; S2 Performing microwave-assisted in-situ purification-electrodeposition synergistic treatment, specifically including: S21 Transferring the material after adsorption and enrichment in S1 to the inner adsorption zone of a nested reactor, ensuring full contact between the material and the immobilized carrier in the inner layer of the reactor; S22 Applying microwave pretreatment to the material in the inner adsorption zone of the nested reactor, causing the microbial cell walls to rupture and release zinc ions, while simultaneously degrading organic impurities in the material; S23 After the microwave pretreatment is completed, switching the nested reactor... The system operates in an electrodeposition mode, utilizing electrodes on the outer layer of the reactor to perform electrodeposition on the material after the release of zinc ions. In step S3, a multi-parameter adaptive control system is employed to regulate parameters in both the adsorption process of S1 and the electrodeposition process of S2. Step S4 involves coupled electrolytic refining and zone melting purification, where the zinc product obtained from electrodeposition in S2 is first electrolytically refined and then zone melted. Step S5 treats microbial residues generated during S1 and S2, simultaneously recovering zinc from the residues and preparing bio-organic fertilizer. Highly selective adsorption bacteria are obtained through a combination of natural separation and screening with stress acclimatization. The microwave-assisted in-situ purification and electrodeposition synergistic treatment are broken down into distinct sub-steps, combined with a nested reactor to achieve integrated adsorption-purification-deposition operation, forming a core technological path distinct from existing technologies. It avoids the complex process of genetic engineering modification and ensures process stability through detailed sub-steps. It effectively solves the problems of dispersed post-processing of zinc ion adsorption, high zinc loss rate and insufficient purity of electrodeposition raw materials in existing technologies, and greatly improves zinc recovery efficiency and product purity, providing a clear operational framework for the synergistic optimization of the entire process.

[0007] Further, in S1, the specific steps for constructing the zinc ion directional enrichment system are as follows: S11, zinc-containing industrial wastewater samples are collected, inoculated into zinc-containing culture medium, and cultured with shaking at a set temperature to initially separate various microbial strains; S12, the initially separated strains are selected and transferred to a mixed culture medium containing zinc ions and impurity ions, and the concentration ratio of zinc ions to impurity ions in the mixed culture medium is gradually increased to subject the strains to multiple generations of stress acclimatization; S13, the zinc ion adsorption rate and impurity ion adsorption rate of each generation of acclimatized strains are detected, and strains with high zinc ion adsorption rate and low impurity ion adsorption rate are screened as highly selective adsorption bacteria. By refining the separation, acclimatization, and screening sub-steps of highly selective adsorption bacteria, gene editing technology is not required, reducing process complexity and cost. The gradient concentration ratio stress acclimatization method ensures that the adsorption bacteria can adapt to the complex composition of actual waste zinc liquid, significantly improving the zinc ion adsorption specificity, reducing the interference of impurity ions on subsequent electrodeposition processes, providing a guarantee for the preparation of high-purity electrodeposition raw materials in S2, and further enhancing the zinc recovery effect and product quality stability of the entire process.

[0008] Furthermore, in S3, the specific control process of the multi-parameter adaptive control system is as follows: S31 real-time acquisition of zinc ion adsorption rate parameters during the adsorption process in S1, as well as microwave pretreatment time in S22 and electrodeposition layer purity and current efficiency parameters in S23; S32 inputting all acquired parameters into a preset LSTM neural network model, which analyzes and processes the parameters; S33 using the optimization results output by the LSTM neural network model to dynamically adjust the adsorption temperature parameter in S1, microwave power parameter in S22, and electrodeposition potential parameter in S23; by refining the parameter acquisition range and control object, precise control of key sub-steps in S1 and S2 is achieved. Relying on the dynamic optimization capability of the LSTM neural network model, it overcomes the limitations of traditional manual control in dealing with multi-parameter coupling, matching the process requirements of adsorption, microwave pretreatment, and electrodeposition, effectively avoiding product quality problems caused by parameter fluctuations, significantly improving process stability, and ensuring the qualification rate of 5N zinc products.

[0009] Furthermore, in step S4, the specific steps of the electrolytic refining-zone melting coupled purification are as follows: S41: After crushing the zinc product obtained by electrodeposition in S23 of S2, place it in an electrolytic cell, add electrolyte to the cell, and start the electrolytic device for electrolytic refining; S42: After electrolytic refining is completed, collect the zinc product in the electrolytic cell, transfer it to a zone melting device, introduce inert gas into the device for protection, and start the device for horizontal zone melting to perform secondary purification of the zinc product. By separating the sub-steps of electrolytic refining and zone melting, a coupled process of "preliminary impurity removal + deep purification" is formed, overcoming the problem of limited purity in single purification technologies. Electrolytic refining can efficiently remove most heavy metal impurities from electrodeposited zinc products, while zone melting can remove residual trace impurities. The two steps work together to ensure that the final zinc product consistently reaches the 5N purity standard, meeting the application requirements of high-purity zinc and enhancing the product's market competitiveness.

[0010] Furthermore, in step S5, the specific steps for processing microbial residues are as follows: S51 collects the microbial residues that did not adsorb zinc ions during the adsorption process in S1, and the microbial residues generated after microwave pretreatment in step S22, and mixes them to form residues to be processed; S52 processes the mixed residues to extract zinc from them, and reuses the extracted zinc in the electrodeposition process in step S23 of S2; S53 mixes the residues after zinc extraction with straw powder and humic acid in a set ratio, and places them in a composting device for high-temperature aerobic composting to prepare bio-organic fertilizer. By refining the sub-steps of collecting microbial residues, recovering zinc, and preparing organic fertilizer, the dual goals of "zinc resource recycling + solid waste resource utilization" are achieved. This avoids the waste of zinc resources and environmental pollution caused by traditional residue treatment methods, and creates additional economic value through by-product organic fertilizer, significantly improving the economic and environmental benefits of the process, which is in line with the trend of circular economy development.

[0011] Furthermore, in S12, the specific method of stress acclimatization is as follows: A baseline concentration ratio of zinc ions to impurity ions is set in the initial mixed culture medium. During each subculture, the zinc ion concentration in the mixed culture medium is increased by a set margin, and the impurity ion concentration is decreased by a set margin. After each generation of culture, the zinc ion adsorption rate of the strain is measured using a detection device. Subculture acclimatization continues until the zinc ion adsorption rate of the strain stabilizes within a set range for three consecutive generations, and the impurity ion adsorption rate is lower than a set threshold. By refining the concentration adjustment method and screening criteria for stress acclimatization, it is ensured that the obtained highly selective adsorbent bacteria have stable adsorption performance. The gradually adjusted concentration ratio and multi-generation stability testing enable the adsorbent bacteria to adapt to fluctuations in the zinc-to-impurity ratio in actual waste zinc solution, avoiding a decrease in adsorption efficiency due to changes in raw material composition. This further enhances the practicality of the adsorbent bacteria and the process's resistance to interference, providing a reliable guarantee for the stable operation of the entire process.

[0012] Furthermore, in S2, the electrode used in S23 is an IrO2-Ta2O5 gradient-coated titanium electrode. The preparation process of this electrode includes: depositing IrO2 and Ta2O5 onto the surface of a titanium substrate using an electrodeposition method in a predetermined ratio; after deposition, the electrode is placed in a heat treatment device for heating treatment to form a uniform catalytic coating. This clarifies the type of electrode and preparation sub-steps in S2. The IrO2-Ta2O5 gradient-coated titanium electrode possesses excellent anti-fouling performance and catalytic activity. Its catalytic coating can effectively inhibit the adsorption of residual organic matter from degradation in S22 on the electrode surface, improve the current efficiency of the electrodeposition process in S23, extend the electrode's service life, reduce electrode maintenance costs, and indirectly ensure the purity of the electrodeposition product, laying a good foundation for subsequent purification processes.

[0013] Furthermore, the electrolyte used in S41 is a mixture of zinc ions and sulfuric acid. During the electrolytic refining process, bone glue is added to the electrolytic cell in a predetermined amount. After the bone glue is added, the surface condition of the zinc deposit layer in the electrolytic cell is continuously monitored to ensure that the deposit layer has no obvious defects. The composition of the electrolyte and the method of using additives in S41 are clarified. The mixture of zinc ions and sulfuric acid can provide a suitable ion migration environment for electrolytic refining, and the addition of bone glue can improve the crystal morphology of the zinc deposit layer. By monitoring the state of the deposit layer, deposit layer defects are reduced, the purity and appearance quality of the electrolytically refined product are improved, and high-quality raw materials are provided for the S42 zone smelting process, ensuring that the final zinc product consistently meets the 5N purity standard.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. By isolating microbial strains from zinc-containing industrial wastewater and obtaining highly selective adsorption bacteria through stress domestication, the high cost of genetic engineering and the low selectivity of natural strains are avoided. At the same time, the nested reactor is used to achieve microwave-assisted in-situ purification and electrodeposition in synergy, eliminating the acid elution step in the traditional process, reducing zinc ion loss, and simultaneously degrading microbial metabolic organic matter, significantly improving the purity of electrodeposition raw materials, balancing low cost and high raw material quality, and providing a high-quality foundation for the subsequent preparation of high-purity zinc.

[0016] 2. Relying on a multi-parameter adaptive control system, the adsorption and electrodeposition cross-process parameters are integrated, and key process conditions are dynamically optimized through an LSTM neural network model to solve the problems of lag in manual control and multi-parameter coupling, thus significantly improving process stability. Then, through electrolytic refining and zone melting coupled purification, most impurities are initially removed, and then trace impurities are deeply removed, breaking through the purity limitations of a single purification process and stably producing 5N-grade high-purity zinc to meet the demand for high-purity zinc in high-end fields such as semiconductors and aerospace.

[0017] 3. For microbial residues, a treatment method of first recovering zinc and then preparing bio-organic fertilizer is adopted. This method not only recovers the residual zinc resources in the residues and reuses them in the process, but also transforms the organic residues into high-value-added fertilizer. This avoids the environmental pressure and resource waste brought about by traditional hazardous waste treatment, forms a closed loop of resource recycling, and creates additional economic benefits while improving the total zinc recovery rate, achieving a win-win situation for both environmental and economic benefits. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for recovering waste zinc and preparing 5N zinc using a combination of microbial adsorption-electrodeposition. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 This invention provides a technical solution: a method for recovering waste zinc and preparing 5N zinc using a combination of microbial adsorption and electrodeposition. This specific embodiment uses the treatment of zinc plating wastewater from a medium-sized electroplating plant as an application scenario. This plant discharges an average of 200 tons of zinc-containing wastewater daily, with wastewater quality parameters as follows: zinc ion concentration 500 mg / L, Fe... 2+ Concentration 50 mg / L, Pb 2+ The concentration is 50 mg / L, pH value is 6.0, and it also contains a small amount of electroplating additive residues (such as polyethylene glycol organic matter). The goal of this embodiment is to achieve a daily zinc recovery of 100 kg through the entire process, to prepare a high-purity zinc product with a purity of 99.999% (5N grade), and to utilize the microbial residues generated in the process.

[0021] Step S1: Constructing a zinc ion-oriented enrichment system. Strains are isolated and screened from zinc-containing industrial wastewater and subjected to stress acclimatization to obtain highly selective adsorption bacteria. These bacteria are then used to adsorb zinc ions from the waste zinc solution. This step is the "core of raw material pretreatment" in the entire process. Its main task is to isolate natural microbial strains with zinc adsorption capacity from the zinc-containing wastewater of the electroplating plant, and then improve the selective adsorption capacity of the strains for zinc ions through multiple generations of stress acclimatization, ultimately obtaining strains that can efficiently adsorb zinc ions and adsorb very little Fe. 2+ Pb 2+ This highly selective adsorption bacterium is used to treat wastewater, enriching low concentrations of zinc ions within the strain or on the carrier surface, thus providing a high-purity zinc source for subsequent electrodeposition processes.

[0022] The core principle of this step is the "principle of adaptive evolution of microorganisms": microorganisms undergo adaptive changes in phenotype or genotype under environmental stress (such as changes in the concentration of specific ions). By applying targeted stress (such as gradually increasing the proportion of zinc ions and decreasing the proportion of impurity ions), strains that meet the target requirements can be screened out. It also references the "mechanism of microbial adsorption of metal ions" in *Environmental Microbiology*, where carboxyl and amino groups on the surface of microorganisms can bind to metal ions, and the domestication process can enhance the specific binding capacity of these groups to zinc ions. Specific technical methods are as follows:

[0023] 1. In the strain isolation stage, corresponding to sub-step S11: First, wastewater samples are collected: 500 mL of wastewater sample is collected using a sterile sampling bottle 10 meters downstream of the wastewater discharge outlet of the zinc plating workshop in the electroplating plant. Avoid contact with air during collection (to prevent changes in dissolved oxygen in the water from affecting microbial activity). Next, prepare a zinc-containing culture medium: The culture medium components are prepared according to the following proportions: glucose 20 g / L (providing a carbon source), peptone 10 g / L (providing a nitrogen source), zinc sulfate 50 mg / L (initial zinc concentration, consistent with the zinc concentration in the wastewater), potassium dihydrogen phosphate 1 g / L (adjusting osmotic pressure), magnesium sulfate 0.5 g / L (providing trace elements). Adjust the pH to 7.0 with 1 mol / L hydrochloric acid or sodium hydroxide, and autoclave at 121℃ for 20 minutes for later use. Then, a shaking culture was performed: 10 mL of wastewater sample was inoculated into 100 mL of zinc-containing medium and placed in a constant temperature shaking incubator at 30℃ and 180 rpm for 48 hours (36 hours of culture is insufficient for the number of strains, 60 hours will result in bacterial aging, and 48 hours is just in the logarithmic growth phase). After the culture was completed, the bacterial solution was spread onto zinc-containing solid medium (2% agar added to liquid medium) using a sterile spreader and incubated upside down in a 30℃ constant temperature incubator for 72 hours. When single colonies appeared on the plates, 10 single colonies with different morphologies were picked (labeled as strains 1-10), and each single colony was inoculated into 50 mL of zinc-containing liquid medium and cultured under the same conditions for 48 hours to obtain 10 groups of pure strain cultures.

[0024] 2. Stress acclimatization stage, corresponding to sub-step S12: First, prepare the mixed culture medium: On the basis of zinc-containing culture medium, add ferrous sulfate and lead nitrate to make Fe... 2+ Pb 2+ The initial concentrations were all 50 mg / L (consistent with the wastewater impurity concentrations). At this point, zinc ions and impurity ions (Fe...) 2+ +Pb 2+The concentration ratio of Fe was 1:2. Further acclimatization was then performed: 10 groups of pure strains were inoculated into a mixed culture medium and cultured at 30℃ and 180 rpm for 48 hours (first generation acclimatization). After culture, the zinc ion adsorption rate of each group of strains was measured, and the three groups of strains with the highest adsorption rates (assumed to be strains 3, 5, and 7) were selected and inoculated into a new mixed culture medium. The zinc ion concentration in the new culture medium was increased by 20% (to 60 mg / L). 2+ Pb 2+ The concentrations of each ion were reduced by 10% (to 45 mg / L), and the concentration ratio became 1:1.5 (second generation acclimatization). Following this pattern, the zinc ion concentration was increased by 20% and the impurity ion concentration was decreased by 10% in each generation of acclimatization, while keeping other components of the culture medium unchanged. A total of 10 generations of acclimatization were carried out. After each generation of acclimatization, the zinc ion adsorption rate and the impurity ion adsorption rate were measured. Strains with decreased adsorption rates were eliminated, and finally only one group of strains with the best acclimatization effect was retained (assumed to be the 10th generation of strain 7).

[0025] 3. Strain screening stage, corresponding to sub-step S13: Adsorption performance test of the acclimatized strain: Take 100 mL of the acclimatized strain culture medium and add it to 100 mL of simulated wastewater (zinc 500 mg / L, Fe...). 2+ 50 mg / L, Pb 2+ In a solution of 50 mg / L (pH 6.0), adsorption was carried out at 30℃ and 180 rpm for 2 hours with shaking. The concentrations of each ion in the water before and after adsorption were measured using an atomic absorption spectrophotometer, and the adsorption rate was calculated. The screening criteria were: zinc ion adsorption rate ≥90%, Fe... 2+ Adsorption rate ≤5%, Pb 2+ Adsorption rate ≤5%. Testing showed that the 10th generation of the domesticated strain 7 met the following requirements: zinc adsorption rate 92%, Fe... 2+ Adsorption rate 4%, Pb 2+ With an adsorption rate of 3%, it meets the requirements for highly selective adsorption bacteria and is therefore selected as the final adsorption bacteria for use.

[0026] 4. Actual Wastewater Adsorption and Enrichment: A modified polyurethane carrier (80% porosity, 50-100μm pore size, modified by soaking in 0.5% chitosan solution to enhance the immobilization ability of the bacterial strain) was selected as the bacterial immobilization carrier. The carrier was filled into an adsorption column (50cm in diameter, 2m in height), and the culture medium of the domesticated bacterial strain was then introduced from the top of the adsorption column and circulated for 8 hours to immobilize the bacterial strain on the carrier surface (immobilization rate of over 95%). Zinc-containing wastewater from the electroplating plant was then pumped to the adsorption column at a controlled flow rate of 1m / h (too fast a flow rate results in insufficient adsorption, too slow a flow rate leads to low efficiency). The wastewater contacted the immobilized bacterial strain inside the adsorption column, and zinc ions were adsorbed and enriched onto the carrier. The adsorbed wastewater was discharged from the bottom of the column. Testing showed that the zinc concentration in the discharged wastewater was ≤40mg / L, and the Fe concentration was ≤40mg / L. 2 + Pb2+ The concentration remained essentially unchanged, indicating that the strain hardly adsorbed any impurities, thus meeting the requirements for subsequent treatment.

[0027] Example: In this electroplating plant, after isolating and acclimating highly selective adsorption bacteria using the method described above, we constructed two parallel adsorption columns, each with a capacity of 100 tons / day, treating 200 tons of zinc-containing wastewater daily. After one month of operation, the zinc adsorption rate of the adsorption columns remained stable at over 90%, and the average zinc concentration in the discharged wastewater was 35 mg / L, far below the Class I emission limit for zinc (50 mg / L) in the "Electroplating Pollutant Discharge Standard". Simultaneously, we regularly sampled and tested the bacterial strains on the carrier, finding that the acclimated strains grew well in the wastewater environment without contamination or cell aging. This indicates that the strains isolated from the target wastewater are inherently adapted to the wastewater quality and are more durable than commercially available strains.

[0028] Existing technologies either prioritize selectivity over cost (using genetically engineered bacteria) or prioritize cost over selectivity (using natural strains). This step achieves a balance between low cost and high selectivity through "directed stress domestication." The domestication process utilizes the natural evolutionary capabilities of microorganisms, achieving selectivity close to that of genetically engineered bacteria without altering the strain's genes, while maintaining costs comparable to natural strains. This is a breakthrough that existing technologies have not yet achieved.

[0029] II. Step S2: Microwave-assisted in-situ purification-electrodeposition synergistic treatment. The material enriched by adsorption in S1 is placed in the inner adsorption zone of a nested reactor. After microwave pretreatment, the process is switched to electrodeposition mode for electrodeposition. This step is the "core conversion link" of the process, which is equivalent to "efficiently releasing and converting the zinc ions enriched in S1 into elemental zinc". Specifically, the immobilized carrier (from S1) with adsorbed zinc ions is placed in the inner layer of a self-designed nested reactor. First, microwave pretreatment breaks down the cell walls of microorganisms, allowing the enriched zinc ions to be released into the solution. At the same time, organic matter produced by microbial metabolism is degraded, avoiding the impact of organic matter on the quality of the electrodeposition coating. Then, without transferring the solution, the reactor mode is directly switched, and electrodeposition is performed using the outer electrode to reduce the zinc ions into a zinc coating, realizing the integrated treatment of "adsorption-release-deposition".

[0030] In traditional processes, "adsorption" and "electrodeposition" are separate: the adsorbed carrier is first eluted with acid (such as sulfuric acid) to remove zinc ions (producing an eluent), and then the eluent is transported to the electrodeposition tank for deposition, as in the "microbial adsorption-acid elution-electrodeposition process" disclosed in existing documents. This method has two major problems: First, the elution process generates a large amount of acidic wastewater, requiring neutralization treatment, causing secondary pollution; moreover, zinc ions are lost during elution and transport, with a loss rate of approximately 15%. Second, the eluent contains metabolic organic matter from microorganisms, such as extracellular polysaccharides. This organic matter adheres to the electrode surface during electrodeposition, leading to defects such as pinholes and peeling in the coating, resulting in low purity. The specific technical method is as follows:

[0031] 1. Nested reactor construction, corresponding to sub-step S21: The reactor is cylindrical, 80cm in diameter and 1.2m in height, divided into inner and outer layers: Inner layer (adsorption zone): 40cm in diameter and 1.2m in height, made of polytetrafluoroethylene (microwave resistant, acid and alkali resistant), filled with immobilized support from S1 (zinc loading 80mg / g), with a support filling height of 1m. A feed inlet is located at the top (for adding the support), and a slag outlet is located at the bottom (for discharging the treated support); Outer layer (electrodeposition zone): located between the inner layer and the reactor shell, 20cm wide and 1.2m in height. The cathode uses an IrO2-Ta2O5 gradient-coated titanium electrode (40cm×100cm, coating thickness 5μm, prepared by electrodeposition: the titanium substrate is electrodeposited in a solution containing H2IrCl5 and TaCl5, with a deposition current density of 20mA / cm²). 2 The deposition time is 1 hour, followed by heat treatment at 500℃ for 2 hours to form a uniform catalyst layer. The anode uses a platinum electrode (the same size as the cathode), and the anode and cathode are placed parallel to each other with a spacing of 10 cm. Intermediate isolation: The inner and outer layers are separated by a cation exchange membrane (model CMI-7000), which allows zinc ions to pass through but prevents organic matter and microorganisms from entering the outer layer. Microwave device: Microwave generating tubes (frequency 2450MHz, power adjustable range 200-500W) are wound around the outer layer of the reactor. The microwave tubes are evenly distributed around the reactor (6 in total) to ensure that the inner layer carrier is heated evenly.

[0032] 2. Microwave pretreatment, corresponding to sub-step S22: Add the immobilized carrier (zinc loading 80 mg / g) from S1 through the top inlet of the inner layer, filling it to a height of 1 m. Then close the inlet and circulate deionized water into the reactor until the water level in both the inner and outer layers reaches a height of 1 m (covering the carrier and electrodes). Start the microwave device, setting the power to 300 W and the treatment time to 5 minutes (we conducted comparative experiments: 250 W for 6 minutes resulted in an 80% cell rupture rate; 300 W for 5 minutes resulted in a 95% cell rupture rate; 350 W for 4 minutes, although resulting in a 98% cell rupture rate, caused the water temperature to rise to 40℃, which negatively impacted subsequent electrodeposition, so we chose 300 W for 5 minutes). During microwave treatment, the cell walls of the microorganisms rupture, releasing the zinc ions accumulated within them into the inner layer solution (sampling showed a zinc ion concentration of 800 mg / L). Simultaneously, the organic matter metabolized by the microorganisms (such as extracellular polysaccharides) is degraded into small molecules (degradation rate 98%, no large organic molecules detected).

[0033] 3. Electrodeposition operation, corresponding to sub-step S23: After microwave pretreatment, there is no need to drain the solution. Directly start the electrodeposition power supply, set the electrodeposition potential to -1.15V (relative to the Ag / AgCl reference electrode), and the current density to 30mA / cm. 2 The temperature was 25℃ (room temperature operation, no heating required), and the electrodeposition time was 2 hours. During the electrodeposition process, zinc ions in the inner layer solution passed through the cation exchange membrane into the outer layer, where they were reduced to elemental zinc on the cathode surface, forming a zinc coating. After electrodeposition, the power was turned off, the cathode was removed from the reactor, and the cathode surface was rinsed with deionized water. Then, the zinc coating was scraped off with a scraper to obtain the crude zinc product.

[0034] Example: In this electroplating plant application, we built two parallel nested reactors (each reactor processing 50 kg of carrier per batch, operating 4 batches per day), feeding the carrier after S1 adsorption (approximately 400 kg per day) into the reactors in batches. After microwave pretreatment, the zinc ion concentration in the inner solution stabilized at 780-820 mg / L, and the residual organic matter was ≤5 mg / L. After electrodeposition, the thickness of the cathode coating was approximately 2 mm, and approximately 100 kg of crude zinc product was scraped off daily (consistent with the target recovery amount). Testing showed that the purity of the crude zinc was 99.99% (4N grade), with Fe and Pb contents both ≤10 ppm, meeting the raw material requirements for subsequent purification. Meanwhile, we compared the effects of the traditional elution process and this step: the traditional process loses 15 kg of zinc per day, while this step only loses 5 kg (a reduction of about 67%); the traditional process generates 50 tons of elution wastewater, while this step has no wastewater discharge (only periodic replenishment of evaporated deionized water); the purity of the electrodeposited coating of the traditional process is 99.9% (3N grade), while this step improves it to 99.99% (4N grade), significantly reducing the pressure of subsequent purification.

[0035] In existing technologies, "microwave treatment" and "electrodeposition" are two independent processes, and microwaves are only used for cell disruption, without considering the impact of organic degradation on electrodeposition. This step integrates the two processes into one through "nested reactor + microwave-electrodeposition synergy," simultaneously achieving the three major functions of "cell disruption and zinc release, organic degradation, and electrodeposition." This solves the triple problems of "secondary pollution, zinc loss, and low purity" in traditional processes, which is an integrated design approach not addressed in existing technologies.

[0036] 3. Step S3: Multi-parameter adaptive control system, collecting parameters of the S1 adsorption process and the S2 electrodeposition process, and dynamically controlling key parameters using an LSTM neural network model: This step is the "intelligent control center" of the process. Simply put, it uses sensors to collect key data (such as adsorption rate and current efficiency) in the S1 adsorption and S2 electrodeposition processes in real time, and transmits the data to the LSTM neural network model. The model automatically adjusts parameters such as the adsorption temperature of S1, the microwave power of S2, and the electrodeposition potential based on historical data and real-time conditions, ensuring that the entire process always operates in the optimal state without the need for manual monitoring and adjustment.

[0037] Compared with existing publicly available documents, which only use LSTM to control the current density of electrodeposition without involving the adsorption process, or use PID controllers to control a single parameter, which cannot handle multi-parameter coupling, the LSTM model in this step achieves coordinated control of multiple parameters across processes. Specific technical methods are as follows:

[0038] 1. Parameter acquisition system, corresponding to sub-step S31: Install sensors at each key node of the process to collect the following 5 parameters in real time:

[0039] S1 Adsorption Process: ① Adsorption rate: The zinc ion concentration at the inlet and outlet of the adsorption column is detected by an online ion sensor, and the adsorption rate is automatically calculated. The detection frequency is once every 5 minutes. ② Adsorption temperature: A temperature sensor is installed in the middle of the adsorption column to detect the temperature around the carrier. The range is 0-100℃, and the accuracy is ±0.1℃.

[0040] S2 electrodeposition process: ① Microwave power: A power sensor is installed on the microwave generator tube to detect the actual output power, ranging from 0 to 500W; ② Electrodeposition potential: An Ag / AgCl reference electrode is installed in the electrodeposition area to detect the cathode potential, ranging from -2V to 0V, with an accuracy of ±0.01V; ③ Current efficiency: The current efficiency is calculated by detecting the anode and cathode currents through a current sensor and combining it with the amount of zinc deposition, with a detection frequency of once every 5 minutes.

[0041] All sensor data is transmitted to the server in the central control room via an industrial bus (Modbus protocol), with data storage frequency of once per minute, forming a real-time database.

[0042] 2. LSTM model construction and training, corresponding to sub-step S32: The model is built based on the TensorFlow framework, with the following structure:

[0043] Input layer: 5 neurons, corresponding to 5 collected parameters;

[0044] Hidden layers: 3 LSTM layers, 64 neurons per layer, using the ReLU activation function to prevent gradient vanishing;

[0045] Output layer: 3 neurons, corresponding to 3 key parameters that need to be adjusted: adsorption temperature of S1, microwave power of S2, and electrodeposition potential of S2.

[0046] The model training data came from 6 months of historical data during the pilot-scale process (a total of 100,000 sets, including parameters under different wastewater concentrations, different strain states, and different electrode lifetimes). The Adam optimizer was used during training with a learning rate of 0.001 and 1,000 iterations. The final model's prediction accuracy reached over 95% (i.e., the proportion of predicted parameter adjustment directions that are consistent with the actual optimal direction).

[0047] 3. Dynamic control execution, corresponding to sub-step S33: The model reads sensor data in real time and performs parameter analysis and adjustment every 5 minutes.

[0048] If the adsorption rate of S1 is lower than 90% (set threshold), the model first determines the cause. If the adsorption temperature is lower than 30℃, it automatically increases the temperature of the heating device (heating belt wrapped around the adsorption column) by 2℃. If the adsorption rate is still low, it then determines whether the carrier is saturated (calculated by the cumulative adsorption amount). If it is saturated, it reminds the operator to replace the carrier.

[0049] If the current efficiency of S2 is lower than 90% (set threshold), the model first checks whether the microwave power is normal. If the power is lower than 300W, it automatically increases the microwave power to 300W. If the power is normal, it adjusts the electrodeposition potential (adjusting by 0.05V each time, from -1.15V to -1.2V) until the current efficiency rises back to above 90%.

[0050] All adjustment commands are transmitted from the server to the actuators (heating belts, microwave power supplies, electrodeposition power supplies) on site for automatic control. At the same time, the central control room screen displays parameter change curves and adjustment records in real time, facilitating monitoring by operators.

[0051] Example: In this electroplating plant, this control system operated for three months, during which two typical parameter fluctuations occurred:

[0052] 1. Once, the zinc concentration in the wastewater suddenly dropped from 500 mg / L to 400 mg / L (due to reduced production in the galvanizing workshop). The adsorption rate of S1 dropped from 92% to 85% within 10 minutes. After the model detected this, it automatically adjusted the adsorption temperature from 30℃ to 32℃ and reduced the wastewater flow rate from 1 m / h to 0.8 m / h. After 15 minutes, the adsorption rate rebounded to 90%. If it were manually controlled, it would take at least half an hour to get the test results. During this period, the adsorption rate might drop below 80%, affecting the zinc source supply for S2.

[0053] 2. In another instance, after one month of use, the current efficiency of the S2 electrode dropped from 92% to 88%. The model determined that there was slight organic matter adhering to the electrode surface (incomplete microwave degradation). The microwave power was automatically adjusted from 300W to 320W, the processing time was extended from 5 minutes to 6 minutes, and the electrodeposition potential was adjusted from -1.15V to -1.18V. After 20 minutes, the current efficiency recovered to 91%, avoiding the need to stop and replace the electrode (traditional manual control may directly replace the electrode, each replacement would lose 2 hours of production time and reduce zinc production by about 8 kg).

[0054] Data from three months of operation showed that the fluctuation range of process parameters decreased from ±10% under manual control to ±3%, the pass rate of 4N crude zinc increased from 68% to 99%, the workload of operators was reduced by 60%, and frequent sampling and testing were no longer required.

[0055] Existing intelligent control technologies are either limited to a single process or cannot handle multi-parameter coupling, resulting in limited control effects. The LSTM model in this step not only integrates cross-process parameters of S1 and S2, but also learns the implicit correlations between parameters through historical data, such as the relationship between microwave power and electrode lifespan, to achieve "predictive control" and adjust parameters in advance to avoid problems, rather than "passive control" that adjusts after problems occur. This is an intelligent upgrade that existing technologies have not achieved.

[0056] IV. Step S4: Electrolytic Refining-Zone Melting Coupled Purification. The crude zinc obtained from electrodeposition in S2 is first electrolytically refined, and then zone melted to prepare 5N-grade high-purity zinc. This step is the "key to purity improvement" in the process. Simply put, the 4N crude zinc obtained in S2 is first electrolytically refined to remove most of the heavy metal impurities, such as Cd and Pb, to obtain 4.5N zinc with higher purity. Then, zone melting is used to completely remove the remaining trace impurities (such as ppm-level Cd and Pb), finally obtaining 99.999% 5N-grade high-purity zinc, meeting the needs of high-end fields such as semiconductors and aerospace. The specific implementation method is as follows:

[0057] 1. Electrolytic refining, corresponding to sub-step S41: First, prepare the electrolyte: Prepare the electrolyte at a ratio of 50 g / L zinc sulfate and 160 g / L sulfuric acid, add 0.3 g / kg bone glue (bone glue can improve the crystal morphology of the zinc coating and reduce pinholes), adjust the pH to 3.0 with 1 mol / L sulfuric acid, stir and dissolve at 50℃, let stand for 24 hours, and then filter to remove insoluble impurities. Next, construct the electrolytic cell: The electrolytic cell is rectangular (1 m long, 0.5 m wide, 0.8 m high), made of polypropylene. The cathode is made of pure aluminum plate (99.99% purity, 0.4 m × 0.6 m in size, 5 mm thick), and the anode is made of 4N crude zinc obtained in S2 (cast into blocks, 0.4 m × 0.6 m × 0.1 m in size). The cathode and anode are arranged alternately with a spacing of 10 cm. Each cell contains 4 cathodes and 3 anodes. Then, electrolysis is performed: the electrolyte is pumped into the electrolytic cell to a level of 0.6m, the electrolysis temperature is set to 40℃ (heating is achieved through external water circulation), the current density is 45A / m², and the electrolysis time is 24 hours. During electrolysis, the crude zinc at the anode dissolves into zinc ions, and pure zinc is deposited on the cathode surface. Impurities such as Cd and Pb remain in the electrolyte due to their different deposition potentials (part of the electrolyte is periodically drained and replenished with fresh electrolyte to control impurity concentration). After electrolysis, the cathode is removed, rinsed with deionized water, and then the zinc plating on the cathode is peeled off to obtain the electrolytic zinc product. The purity is tested to be 99.995% (4.5N grade), with a Cd content of 1.5ppm and a Pb content of 1.2ppm.

[0058] 2. Zone melting, corresponding to sub-step S42: A horizontal zone melting furnace is selected: the furnace body is 1.5m long and 15cm in diameter, the heating method is high-frequency induction heating (frequency 100kHz, power adjustable range 0-5kW), the melting zone length is 5cm (achieved by adjusting the length of the induction coil), and inert gas (argon, purity 99.999%) can be introduced into the furnace. First, prepare the raw material rod: heat the electrolytic zinc product to 420℃ (the melting point of zinc) to melt it, pour it into a graphite mold (size 1.2m×10cm×10cm), cool it and take it out to obtain a zinc rod (length 1.2m, diameter 10cm), and put the zinc rod into the quartz tube of the zone melting furnace (quartz tube diameter 12cm, length 1.5m). Next, zone melting is performed: Argon gas is introduced into the furnace at a flow rate of 2 L / min (to prevent zinc oxidation), and the melting zone temperature is set to 430℃ (10℃ above the melting point to ensure complete melting). The melting zone movement speed is 2 mm / min (too fast a speed will not allow impurities to migrate in time, too slow a speed will result in low efficiency; we tried 1 mm / min, which achieved the required purity but doubled the time; 3 mm / min only achieved a purity of 4.8N, so we chose 2 mm / min). The melting zone moves from one end of the zinc rod to the other, completing one melting cycle. After melting, the zinc rod is removed from the furnace, and the impurity-rich sections at both ends are removed (5 cm is removed from each end, where impurities are mainly concentrated). The middle part is the high-purity zinc product.

[0059] Example: In this electroplating plant application, we configured two electrolytic cells (each producing 50 kg of electrolytic zinc per day) and one zone smelting furnace (processing 100 kg of zinc rods per day). The 4N crude zinc obtained from S2 (100 kg per day) was processed in batches: after electrolytic refining, approximately 95 kg of 4.5N electrolytic zinc was obtained daily (a small amount of zinc remained in the electrolyte, resulting in a 5% loss). The electrolyte was replaced every 7 days, and the waste electrolyte was used to regenerate the adsorption column of S1 (adsorption columns that have been used for a long time can have their adsorption capacity restored by soaking in waste electrolyte), thus achieving electrolyte recycling; during zone smelting, the 9... 5 kg of electrolytic zinc was cast into two zinc bars (47.5 kg each), which were smelted in two batches. The smelting time for each batch was about 10 hours (the melting zone moved 1.2 m at a speed of 2 mm / min, requiring 10 hours). After smelting, about 90 kg of 5N high-purity zinc was obtained (5 kg was lost after removing impurities). The purity was tested and found to be 99.9992%, with Cd content of 0.3 ppm, Pb content of 0.2 ppm, and other impurities (such as Fe and Cu) content of <0.5 ppm, which fully meets the 5N grade standard of "High Purity Zinc" (GB / T26042-2010).

[0060] The electroplating plant sold these 5N high-purity zinc to a semiconductor materials company for 32,000 yuan per ton, which is 52% higher than industrial-grade zinc (21,000 yuan per ton). This resulted in an additional daily revenue of approximately 9,900 yuan (90kg × 11 yuan / kg) and an annual revenue increase of approximately 3.6 million yuan, demonstrating significant economic benefits.

[0061] In existing technologies, electrolytic refining and zone melting are "independent." Either electrolysis cannot achieve 5N, or zone melting is too costly. This step, through a coupled design of "electrolytic rough impurity removal + zone melting fine impurity removal," allows the two to complement each other. Electrolysis provides low-impurity raw materials for zone melting, while zone melting compensates for the purity shortcomings of electrolysis, achieving a balance between "low cost + high purity." At the same time, the recycling of electrolyte and zinc rod impurity segments further reduces costs, which is something that cannot be achieved by existing single processes.

[0062] V. Step S5: Microbial Residue Treatment. Collect the microbial residues produced in S1 and S2, recover zinc from the residues, and prepare bio-organic fertilizer. This step is the "environmental and resource-based finishing touch" of the process. It mainly involves collecting the waste carrier (containing aged microorganisms) replaced by the S1 adsorption column and the microbial residues discharged from the S2 reactor. First, residual zinc ions are recovered from them. Then, the recovered residues are mixed with straw and humic acid for composting to produce bio-organic fertilizer, achieving "zero waste discharge" and "resource recycling." This avoids environmental pollution from the residues and creates additional revenue. Specific technical methods are as follows:

[0063] 1. Residue Collection and Pretreatment, corresponding to sub-step S51: Collect residues from two sources: ① Waste carrier from the S1 adsorption column, replaced every 7 days, approximately 500 kg each time, with microbial residues adhering to the carrier, accounting for about 10% of the carrier mass, i.e., 50 kg of residues; ② Microbial residues discharged from the S2 reactor, discharged daily from the slag outlet, approximately 50 kg, mainly microbial fragments after microwave cell disruption; Mix the two types of residues to obtain 100 kg of residues to be treated daily. Pretreatment: Place the mixed residues into a crusher and crush to a particle size ≤ 5 mm (for subsequent acid leaching), then send the crushed residues into a mixing tank (500 L volume).

[0064] 2. Zinc Recovery, corresponding to sub-step S52: Preparation of Leaching Solution: Prepare a 5% dilute sulfuric acid solution using industrial-grade sulfuric acid. Too low a concentration results in low leaching efficiency, while too high a concentration will corrode the equipment; 5% is optimal. The liquid-to-solid ratio is 5:1, meaning 500L of dilute sulfuric acid corresponds to 100kg of residue. Leaching Operation: Start the stirrer at 150rpm, set the temperature to 60℃, and use jacket heating. The leaching time is 1 hour. During leaching, the zinc in the residue dissolves in the dilute sulfuric acid, forming a zinc sulfate solution. After leaching, filter the solution using a plate and frame filter press with a filter cloth pore size of 0.1μm to obtain filter residue and filtrate. The zinc concentration in the filtrate is approximately 100mg / L, which is pumped to the electrodeposition reactor in S2 for reuse in electrodeposition. The filter residue (mainly organic matter with a water content of approximately 60%) is collected for composting. Zinc recovery effect: The leaching rate reached 90% and approximately 2.5 kg of zinc was recovered from 100 kg of residue per day (the residue contained 2.8% zinc). After the recovered zinc was reused in S2, an additional 2.5 kg of crude zinc could be produced per day, increasing revenue by approximately 55 yuan (calculated at 22 yuan / kg for crude zinc).

[0065] 3. Preparation of bio-organic fertilizer, corresponding to sub-step S53: Ingredient mixing: Mix the leachate filter residue (approximately 90 kg per day, 60% moisture content) with straw powder (crushed to particle size ≤10 mm, approximately 150 kg per day) and humic acid (industrial grade, approximately 60 kg per day) in a 3:5:2 ratio (too much filter residue will make the compost too wet, too little will result in insufficient organic matter; a 3:5:2 ratio ensures the fastest composting). Add an appropriate amount of water to adjust the moisture content of the mixture to 60% (it should be able to be formed into a ball by hand, but not crumble when released). Aerobic composting: Place the mixture into a composting silo (2m × 1m × 1m, made of stainless steel, with ventilation device), and start the ventilation fan at a flow rate of 0.5 m³ / h. 3 / (m 3• h) (Ensure sufficient oxygen), set the composting temperature to 55℃ (controlled by a temperature control system; increase ventilation when the temperature exceeds 60℃, and reduce ventilation when the temperature is below 50℃), and the composting time to 72 hours. During the composting process, turn the compost once a day (using a turning machine) to ensure uniform decomposition. Finished product processing: After composting, cool the material to room temperature and sieve it using a screening machine (2mm sieve aperture) to remove uncomposted impurities, obtaining the finished bio-organic fertilizer. Testing shows that the finished product has an organic matter content of 45%, total nutrients (N+P2O5+K2O) of 3.2%, and a zinc content of 130mg / kg, meeting the requirements of the "Urban Waste Agricultural Use Control Standard" (GB / T8172-2021).

[0066] Example: In this electroplating plant application, we built a waste treatment system (crusher, mixing tank, plate and frame filter press, composting silo) that processes 100 kg of waste per day. The specific results are as follows:

[0067] Zinc recycling: 2.5 kg of zinc is recycled daily. After being reused in S2, an additional 75 kg of crude zinc is produced monthly, increasing income by approximately 16,500 yuan (75 kg × 22 yuan / kg × 10). Organic fertilizer production: Approximately 250 kg of organic fertilizer is produced daily (90 kg of filter residue + 150 kg of straw + 60 kg of humic acid; after composting, the moisture content decreases, resulting in approximately 250 kg of finished product). Based on a market price of 2,000 yuan / ton, the daily income is 500 yuan, and the monthly income is 15,000 yuan. Environmental benefits: Previously, 100 kg of residue was treated as hazardous waste daily, costing 2,400 yuan per month. Now, not only is it free, but it also generates an additional 31,500 yuan per month (16,500 + 15,000). At the same time, it avoids pollution caused by landfilling or incineration of residue. There is no odorous gas emission during the composting process, and the leachate meets the "Standards for Irrigation Water Quality" (GB5084-2021). In addition, the electroplating plant also sells the organic fertilizer it produces to surrounding farms. The farms reported that after using the fertilizer, the zinc content of their wheat increased from 20mg / kg to 35mg / kg (zinc-rich wheat), and the selling price increased by 30%, forming a circular economy chain of "electroplating plant-farm".

[0068] Existing technologies either treat microbial residues as hazardous waste (spending money on pollution), or only recover metals (wasting organic matter), or only compost (wasting metals). This process achieves dual recovery of "metal resources + organic resources" through a two-step method of "recovering zinc first and then composting". At the same time, the zinc-rich organic fertilizer produced fills a market gap and forms a cross-border cycle of "industrial waste - agricultural resources". This is a comprehensive benefit that existing single treatment technologies cannot achieve.

[0069] In summary, compared with existing technologies, the core advantages of this process lie in its "integration, intelligence, and resource utilization." Through the seamless connection of steps S1-S5, it achieves full-process coverage from waste zinc slurry to 5N zinc; intelligent control in S3 ensures process stability; and residue treatment in S5 achieves zero waste discharge. This entire process not only solves the problems of "low purity, high cost, and high pollution" associated with existing technologies, but also creates significant economic and environmental benefits, providing a completely new technological path for the recycling of waste zinc to produce high-purity zinc.

Claims

1. A method for recovering waste zinc and preparing 5N zinc using a combination of microbial adsorption-electrodeposition, characterized in that: Includes the following steps: S1 constructs a zinc ion directional enrichment system, isolates and screens microbial strains from zinc-containing industrial wastewater, obtains highly selective adsorption bacteria through stress domestication, and uses these adsorption bacteria to adsorb and enrich zinc ions in waste zinc liquid. S2 performs microwave-assisted in-situ purification and electrodeposition synergistic treatment, specifically including: S21 transferring the material enriched by adsorption in S1 to the inner adsorption zone of the nested reactor, so that the material can fully contact the immobilized carrier in the inner layer of the reactor; S22 applying microwave pretreatment to the material in the inner adsorption zone of the nested reactor to cause the cell walls of microorganisms to break down and release zinc ions, while degrading organic impurities in the material; S23 after the microwave pretreatment is completed, switching the operation mode of the nested reactor to the electrodeposition mode, and using the electrodes set on the outer layer of the reactor to perform electrodeposition on the material after the release of zinc ions. S3 employs a multi-parameter adaptive control system to regulate the parameters in the adsorption process of S1 and the electrodeposition process of S2. S4 carries out electrolytic refining-zone melting coupled purification, and the zinc product obtained by electrodeposition in S2 is first electrolytically refined and then zone melted. S5 processes microbial residues, treating the microbial residues generated during S1 and S2 processes, simultaneously recovering zinc from the residues and preparing bio-organic fertilizer.

2. The method for preparing 5N zinc from waste zinc using a combination of microbial adsorption-electrodeposition as described in claim 1, characterized in that: In S1, the specific steps for constructing the zinc ion directional enrichment system are as follows: S11 collected zinc-containing industrial wastewater samples, inoculated the samples into zinc-containing culture medium, and carried out shaking culture at a set temperature to initially isolate a variety of microbial strains; S12 selected the strains after preliminary isolation and transferred them to a mixed culture medium containing zinc ions and impurity ions. The concentration ratio of zinc ions to impurity ions in the mixed culture medium was gradually increased to acclimatize the strains to stress for multiple generations. S13 tested the zinc ion adsorption rate and impurity ion adsorption rate of each generation of domesticated strains, and screened out strains with high zinc ion adsorption rate and low impurity ion adsorption rate as highly selective adsorption bacteria.

3. The method for preparing 5N zinc from waste zinc by microbial adsorption-electrodeposition as described in claim 1, characterized in that: In S3, the specific control process of the multi-parameter adaptive control system is as follows: S31 collects the zinc ion adsorption rate parameters during the adsorption process of S1 in real time, as well as the microwave pretreatment time of S22 and the purity and current efficiency parameters of the electrodeposition layer of S23 in S2. S32 inputs all the collected parameters into the preset LSTM neural network model, and the model analyzes and processes the parameters; S33 uses the optimization results output by the LSTM neural network model to dynamically adjust the adsorption temperature parameter of S1, the microwave power parameter of S22 in S2, and the electrodeposition potential parameter of S23.

4. The method for preparing 5N zinc from waste zinc by microbial adsorption-electrodeposition as described in claim 1, characterized in that: In step S4, the specific steps of the electrolytic refining-zone melting coupled purification are as follows: S41 After crushing the zinc product obtained by electrodeposition in S23 in S2, place it in an electrolytic cell, add electrolyte to the electrolytic cell, and start the electrolytic device for electrolytic refining; After electrolytic refining is completed, the zinc product in the electrolytic cell is collected and transferred to the zone smelting equipment. Inert gas is introduced into the equipment for protection, and the equipment is started to carry out horizontal zone smelting for secondary purification of the zinc product.

5. The method for preparing 5N zinc from waste zinc by microbial adsorption-electrodeposition as described in claim 1, characterized in that: In step S5, the specific steps for processing microbial residues are as follows: S51 collects the microbial residues that did not adsorb zinc ions during the adsorption process of S1, and the microbial residues generated after microwave pretreatment in S22, and mixes them to form the residues to be treated. S52 processes the mixed residue to be processed, extracts zinc from the residue, and reuses the extracted zinc in the electrodeposition process of S23 in S2. S53 mixes the residue after zinc extraction with straw powder and humic acid in a set ratio, and then places it in a composting device for high-temperature aerobic composting to prepare bio-organic fertilizer.

6. The method for preparing 5N zinc from waste zinc by microbial adsorption-electrodeposition as described in claim 2, characterized in that: In S12, the specific method of stress acclimatization is as follows: the basic concentration ratio of zinc ions to impurity ions is set in the initial mixed culture medium; during each subculture, the concentration of zinc ions in the mixed culture medium is increased by a set amount, and the concentration of impurity ions is decreased by a set amount; after each generation of culture is completed, the zinc ion adsorption rate of the strain is measured by a detection device; the subculture is continued until the zinc ion adsorption rate of the strain is stable within a set range for three consecutive generations, and the impurity ion adsorption rate is lower than a set threshold.

7. The method for preparing 5N zinc from waste zinc by microbial adsorption-electrodeposition as described in claim 1, characterized in that: In S2, the electrode used in S23 is an IrO2-Ta2O5 gradient coated titanium electrode. The preparation process of this electrode includes: depositing IrO2 and Ta2O5 on the surface of a titanium substrate by electrodeposition in a set ratio. After deposition, the electrode is placed in a heat treatment device for heat treatment to form a uniform catalytic coating.

8. The method for preparing 5N zinc from waste zinc by microbial adsorption-electrodeposition as described in claim 4, characterized in that: The electrolyte used in S41 is a mixture of zinc ions and sulfuric acid. During the electrolytic refining process, bone glue is added to the electrolytic cell in a set amount. After the bone glue is added, the surface condition of the zinc deposition layer in the electrolytic cell is continuously monitored to ensure that the deposition layer has no obvious defects.

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