Zero discharge method for high-salt and high-complexity wastewater in lithium battery industry and integrated treatment system

Abstract

The invention discloses a zero discharge method for high-salt and high-complexity wastewater in the lithium battery industry and an integrated treatment system, and relates to the field of wastewater treatment. The wastewater zero discharge method comprises the following steps: collecting lithium battery wastewater into an adjusting tank, and adjusting water quality and water quantity; adding a composite decomplexing agent composed of ethylenediaminetetraacetic acid salt, sulfite and ferrous sulfate into the adjusted wastewater, and destroying a heavy metal-organic matter complex through a redox and chelation competition effect; adding a sulfide solution into the wastewater subjected to complex breaking, and removing heavy metal sulfide precipitates; adjusting the pH value of the wastewater subjected to primary precipitation to 7.0-7.5, adding modified calcium chloride and polyaluminum chloride into the wastewater, and removing fluoride through precipitation. Through the synergistic effect of complex disassembly, fractional precipitation, enhanced biochemical treatment, catalytic oxidation and membrane separation, deep removal of various pollutants is achieved, the removal rate of heavy metal ions can reach 99.9% or above, and the removal rate of organic matter COD can reach 95% or above.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method and integrated treatment system for zero discharge of high-salt and highly complex wastewater from the lithium battery industry. Background Technology

[0002] With the global energy structure shifting towards low-carbon development, lithium batteries, as a core component of electric vehicles and energy storage systems, are experiencing explosive market growth. According to the "2024 Global Lithium Battery Industry White Paper," global lithium battery shipments reached 1525 GWh in 2023, a year-on-year increase of 35%, with China accounting for over 70% of global lithium battery production. The lithium battery production process generates significant amounts of wastewater, including cathode material preparation (such as ternary materials and lithium iron phosphate), anode coating, electrolyte preparation, and battery cleaning. It is estimated that approximately 500-800 tons of wastewater are generated for every 1 GWh of lithium battery produced.

[0003] Heavy metal ions (such as cobalt and nickel) in lithium battery wastewater have bioaccumulation properties, and long-term accumulation can lead to liver and kidney damage in humans; fluoride can cause soil calcification and plant root damage, and concentrations exceeding 50 mg / L can directly cause plant death; the organic pollutant NMP has reproductive toxicity and threatens human health through the food chain. According to the Ministry of Ecology and Environment's "2023 Key Industry Water Pollution Discharge Report," the fluoride exceedance rate in lithium battery industry wastewater discharge reached 28%, the comprehensive compliance rate for heavy metals was only 72%, and the compliance rate for high-salinity wastewater treatment was less than 60%.

[0004] At the same time, environmental protection policies are becoming increasingly stringent: China's "Water Pollution Prevention and Control Plan" ("Water Ten Measures") clearly requires key industries to achieve zero wastewater discharge by the end of 2025; the EU's "Industrial Emissions Directive" (IED) stipulates that the emission limit for fluoride in wastewater from lithium battery production is 10 mg / L, and the total emission concentration of heavy metals shall not exceed 0.1 mg / L; the domestic industry standard "Water Pollutant Discharge Standard for Lithium Battery Industry" (draft for comments) proposes to set the COD limit in recycled water to below 50 mg / L, conductivity ≤100 μS / cm, fluoride ≤5 mg / L, and heavy metal single factor ≤0.05 mg / L.

[0005] This type of wastewater also exhibits significant complexity and extreme characteristics: (1) The pollutants are diverse and interact with each other. They include heavy metal ions such as cobalt, nickel, lithium, and manganese (concentrations are usually 10-200 mg / L), fluorides (50-300 mg / L), and organic pollutants (COD can reach 1000-3000 mg / L, mainly N-methylpyrrolidone (NMP), ethylene glycol, dimethyl carbonate, etc.). Some heavy metals form stable complexes with organic matter (such as cobalt-NMP complexes), which are difficult to disintegrate by conventional methods. (2) The water quality fluctuates greatly. The wastewater from different processes varies greatly. The wastewater from the positive electrode material is strongly acidic (pH≤2) and rich in fluoride. The wastewater from the negative electrode coating contains high concentrations of NMP and suspended solids (SS≥500mg / L). The electrolyte wastewater contains more than 5% salt (mainly LiPF6 and NaCl), which makes it difficult for traditional single treatment processes to operate stably. (3) Synergistic inhibition of high salt and high toxicity. The synergistic effect of salinity (0.5%-5%) in wastewater with heavy metals and fluorides further exacerbates the difficulty of treatment, and conventional biochemical systems can hardly tolerate it.

[0006] Current lithium battery wastewater treatment technologies are mainly divided into single treatment methods and combined treatment methods, but both have significant limitations: 1. Chemical treatment method Neutralization precipitation method: The pH is adjusted to alkaline (8-11) by adding NaOH or Ca(OH)2, causing heavy metal ions to precipitate as hydroxides. This method can achieve a removal rate of 85%-90% for cobalt and nickel, but it has four major drawbacks: ① The fluoride removal effect is poor (only 30%-50%), requiring the addition of excessive calcium salt (calcium-fluoride molar ratio ≥2:1), resulting in an increase in sludge production of more than 30%; ② Under high pH conditions, lithium easily forms LiOH and dissolves, making lithium resource recovery impossible; ③ The resulting metal hydroxide precipitates have small particle sizes (<5μm) and settling speeds (≤0.1m / h), requiring the addition of large amounts of flocculants (e.g., PAC dosage ≥500mg / L). ④ The heavy metal-organic complex cannot be broken down, resulting in an actual residual concentration of heavy metals exceeding 0.5 mg / L, far exceeding the standard for recycled water.

[0007] Membrane separation method: Early applications of ultrafiltration (UF) and nanofiltration (NF) membranes can retain some large organic molecules and heavy metals, but they have inherent drawbacks: ① Nanofiltration membranes have a rejection rate of less than 50% for monovalent ions (such as Li+, F-), which cannot meet the requirements for reuse; ② The membrane surface is fouled by NMP, suspended solids and complexes, which leads to a decrease in membrane flux of more than 40%, requiring frequent chemical cleaning (2-3 times a week), and the lifespan is only 1-2 years; ③ Under high-salt conditions, the membrane material is easily oxidized and degraded, and the desalination rate continues to decline. After 6 months of operation, the desalination rate is less than 85%.

[0008] 2. Biological treatment method Anaerobic-aerobic process: High-concentration organic matter is degraded in an anaerobic tank (e.g., NMP removal rate 60%-70%), and then further treated in an aerobic tank. However, three major problems exist: ① Lithium battery wastewater often contains high concentrations of salt (such as NaCl and LiPF6) of 0.5%-5%, which leads to the inhibition of microbial activity. When the salinity is >3%, the COD removal rate drops sharply to below 40%. ② Heavy metal ions (concentration ≥10mg / L) have toxic inhibitory effects on microorganisms and require costly chemical pretreatment. ③ The removal rate of recalcitrant organic compounds (such as dimethyl carbonate) is less than 30%, and it cannot remove fluorides and heavy metals.

[0009] 3. Traditional assembly process: The typical process is "neutralization and sedimentation - biochemical treatment - sand filtration - discharge". Although this process can achieve pollutant discharge that meets standards, it has fundamental shortcomings: ① Serious waste of water resources: The treated wastewater only meets the discharge standards (such as COD≤100 mg / L) and cannot be reused in the production process. The water reuse rate is generally less than 30%. ② The problem of secondary pollution is prominent: the sludge produced by chemical precipitation has a water content of over 95% and contains a large amount of calcium fluoride compounds (accounting for over 60%) and unrecovered heavy metals. It is classified as hazardous waste, with landfill costs of 800-1000 yuan / ton, and there is a risk of heavy metal leakage. ③ Incomplete fluoride removal: Traditional processes rely on Ca(OH)2 or CaCl2 to precipitate fluoride ions, which is limited by the solubility product (Ksp=3.45×10). -11 Fluoride residual concentrations are typically 15-20 mg / L, exceeding the standard for reclaimed water (≤5 mg / L). ④ Failure to dismantle complexes leads to failure of subsequent treatment: Cobalt-NMP and nickel-ethylene glycol complexes in wastewater cannot be destroyed in traditional processes, resulting in mutual constraints on the removal rates of heavy metals and organic matter.

[0010] Therefore, there is an urgent need to develop a new method and integrated treatment system for zero-discharge of high-salt and complex wastewater from the lithium battery industry to address current deficiencies and shortcomings. Against this backdrop, the traditional "compliant discharge" model is no longer sufficient, and developing an integrated zero-discharge treatment process has become a pressing technical challenge for the industry. Summary of the Invention

[0011] In view of this, the main objective of the present invention is to provide a method and integrated treatment system for zero discharge of high-salt and highly complex wastewater from the lithium battery industry, in order to at least partially solve the above-mentioned technical problems.

[0012] To achieve the above objectives, as a first aspect of the present invention, a method for zero discharge of high-salt and highly complex wastewater from the lithium battery industry is proposed, comprising the following steps: Wastewater generated during lithium battery production is collected in an equalization tank to adjust the water quality and quantity, thereby adjusting the pH value of the wastewater to 5.0-6.0 and controlling the temperature at 25-30℃. Adding a complex complex-breaking agent composed of ethylenediaminetetraacetate, sulfite and ferrous sulfate to the adjusted wastewater breaks down heavy metal-organic complexes through redox and chelation competition, releasing free heavy metal ions and organic matter. Sulfide solution is added to the wastewater after complex breaking, and the dosage is adjusted in real time according to the heavy metal concentration to remove heavy metal sulfide precipitates; After primary sedimentation, the pH of the wastewater is adjusted to 7.0-7.5, and modified calcium chloride and polyaluminum chloride are added to remove fluoride through precipitation.

[0013] As a second aspect of the present invention, a zero-discharge integrated treatment system for high-salt and highly complex wastewater from the lithium battery industry is also proposed, comprising: The equalization tank is used to contain wastewater generated during the lithium battery production process, and to regulate the water quality and quantity, so that the pH value of the wastewater is adjusted to 5.0-6.0 and the temperature is controlled at 25-30℃. The complex decomposition reactor is used to contain the conditioned wastewater and to add a composite complex decomposing agent composed of ethylenediaminetetraacetate, sulfite and ferrous sulfate, so as to destroy the heavy metal-organic complex through redox and chelation competition, and release free heavy metal ions and organic matter. The primary sedimentation reactor is used to contain the wastewater after complex breaking and to add sulfide solution. The dosage is adjusted in real time according to the heavy metal concentration in order to remove heavy metal sulfide precipitates. The fluoride removal reactor is used to contain wastewater after primary sedimentation, adjust its pH to 7.0-7.5, and add modified calcium chloride and polyaluminum chloride to remove fluoride through precipitation.

[0014] Based on the above technical solution, it can be seen that the zero-discharge method and integrated treatment system for high-salt and highly complex wastewater in the lithium battery industry of the present invention has at least one of the following beneficial effects compared with the prior art: (1) Deep removal of pollutants: This invention achieves deep removal of various pollutants through the synergistic effect of complex disintegration, graded precipitation, enhanced biochemical treatment, catalytic oxidation and membrane separation. The removal rate of heavy metal ions (Co, Ni, Li, Mn) can reach more than 99.9% (residual concentration ≤0.05 mg / L), the removal rate of fluoride can reach more than 99% (residual concentration ≤3 mg / L), the removal rate of organic matter (COD) can reach more than 95% (residual concentration ≤30 mg / L), and the removal rate of salinity can reach more than 99.5%, meeting the stringent standards for recycled water.

[0015] (2) Gradual reuse of water resources: Construct a primary reuse water system (conductivity ≤50μS / cm) and a secondary reuse water system (conductivity ≤100μS / cm). The primary reuse water is used for high-precision processes such as battery cleaning and electrolyte preparation, while the secondary reuse water is used for general processes such as cooling and greening. The water reuse rate is ≥95%, which greatly reduces the amount of fresh water used (saving more than 0.95 tons of fresh water per ton of water).

[0016] (3) Solid waste resource recovery: to realize the resource recovery of heavy metals (Co, Ni, Li), fluorides and salts in sludge, with cobalt and nickel recovery rates ≥95%, lithium recovery rate ≥90%, fluorine recovery rate ≥85%, salt recovery rate ≥98%, and solid waste harmless disposal rate 100%, avoiding secondary pollution, while creating significant economic benefits (solid waste recovery value per ton of wastewater ≥50 yuan).

[0017] (4) Significantly reduced treatment costs: Through agent optimization (synergistic effect of compound complex-breaking agent + modified calcium salt + chelating agent, agent dosage is reduced by more than 30%), membrane life extension (ultrafiltration membrane life is 3-4 years, reverse osmosis membrane life is 5-6 years), and energy recovery (biogas utilization + waste heat from incineration, energy consumption is reduced by more than 25%), the cost of treating 1 ton of wastewater is reduced to 80-100 yuan (150-200 yuan for traditional processes).

[0018] (5) High salt and high toxicity with strong adaptability: The salt-tolerant composite microbial community can tolerate a salinity of more than 5% and a heavy metal concentration of more than 20mg / L. The catalytic ozone oxidation + modified membrane system can effectively treat high concentrations of organic matter and complexes. The process adaptability covers various types of lithium battery wastewater (positive electrode, negative electrode, electrolyte, mixed wastewater).

[0019] (6) Intelligent and stable operation: It integrates online monitoring and PLC intelligent control system, which can respond to water quality and quantity fluctuations in real time, improve the stability of treatment effect by more than 40%, and reduce the difficulty of operation without frequent manual adjustment. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0021] Figure 1 This is a structural block diagram of the integrated zero-discharge treatment system for high-salt and highly complex wastewater in the lithium battery industry, as described in this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0023] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of the invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0024] Existing technologies for treating lithium battery wastewater are inefficient and costly. Our research has revealed the following drawbacks: (1) Lack of complex dismantling technology: Stable complexes formed by heavy metals and organic matter (stability constant K≥10) 5 These pollutants cannot be destroyed by conventional chemical precipitation or biodegradation, making it difficult to improve the pollutant removal rate. (2) Insufficient synergy in the graded removal of pollutants: The removal processes of heavy metals, fluorides, organic matter and high salt interfere with each other. For example, high concentrations of organic matter adsorb on the surface of metal precipitates, reducing precipitation efficiency; calcium fluoride crystals formed by fluoride ions and calcium ions easily encapsulate heavy metal ions, leading to an increase in residual concentration; high salt environment simultaneously inhibits microbial activity and membrane separation performance. (3) Water resource gradient reuse system not constructed: Traditional processes do not carry out gradient reuse according to the different water quality requirements of the production process, resulting in waste of high-quality reuse water or substandard water quality; (4) Low degree of solid waste resource utilization: Heavy metals (cobalt and nickel total 5%-8%) and lithium resources (concentration in wastewater 50-100mg / L) in sludge are not effectively extracted, fluoride is wasted in the form of calcium fluoride compounds, and sludge disposal costs are high. (5) Lack of intelligent control: The process parameters rely on manual experience for adjustment and cannot be optimized in real time according to water quality fluctuations, resulting in unstable treatment effect.

[0025] It is evident that existing technologies suffer from drawbacks such as difficulty in dismantling complexes, incomplete removal of various pollutants, low treatment efficiency in high-salt environments, low water reuse rate, low degree of solid waste resource utilization, high treatment costs, susceptibility to secondary pollution, and lack of intelligent control systems.

[0026] In response to this situation, this invention proposes an efficient, environmentally friendly, and economical integrated treatment process for zero-discharge of high-salt and complex wastewater from the lithium battery industry. Through the synergistic integration of multiple units including "complex dismantling, graded precipitation, enhanced biochemical treatment, advanced oxidation, membrane separation, and solid waste resource recovery," it achieves deep removal of complexed pollutants, heavy metals, fluorides, organic matter, and high salt content from wastewater. Simultaneously, it enables gradient reuse of water resources and resource recovery of solid waste, achieving the goal of zero wastewater discharge.

[0027] Specifically, this invention proposes a method for zero discharge of high-salt, high-complexity wastewater from the lithium battery industry, comprising the following steps: Wastewater generated during lithium battery production is collected in an equalization tank to adjust the water quality and quantity, thereby adjusting the pH value of the wastewater to 5.0-6.0 and controlling the temperature at 25-30℃. Adding a complex complex-breaking agent composed of ethylenediaminetetraacetic acid (such as disodium EDTA), sulfite and ferrous sulfate to the adjusted wastewater can break down heavy metal-organic complexes through redox and chelation competition, releasing free heavy metal ions and organic matter. Sulfide solution is added to the wastewater after complex breaking, and the dosage is adjusted in real time according to the heavy metal concentration to remove heavy metal sulfide precipitates; After primary sedimentation, the pH of the wastewater is adjusted to 7.0-7.5, and modified calcium chloride and polyaluminum chloride are added to remove fluoride through precipitation.

[0028] Therefore, the industrial wastewater from lithium battery production can be treated by regulating, breaking down complexes, removing heavy metals and fluoride in a primary stage, thus solving the shortcomings and deficiencies of existing technologies such as difficulty in dismantling complexes and insufficient synergy in the graded removal of pollutants, and improving the efficiency of pollutant removal, resource recovery and gradient reuse of water resources.

[0029] The step of collecting wastewater into the equalization tank also includes installing a stirring device in the equalization tank, with a stirring speed of, for example, 60-80 r / min, and installing an online monitoring module to monitor pH, COD, heavy metal concentration, salinity, etc. in real time, to ensure that the wastewater is mixed evenly and to provide real-time feedback on water quality data.

[0030] The step of adding the composite complex-breaking agent to the regulated wastewater is carried out in a complex disintegration reactor. The composite complex-breaking agent is preferably composed of disodium ethylenediaminetetraacetate, sodium sulfite, and ferrous sulfate in a mass ratio of 3:2:1.

[0031] The dosage of the composite complex-breaking agent is 300-500 mg / L, the reaction pH is controlled at 2.5-3.5, the reaction time is 60-90 minutes, and the stirring speed is 40-50 r / min.

[0032] The step of adding sulfide solution to the wastewater after complex breaking is carried out in a primary sedimentation reactor.

[0033] The pH value of the primary precipitation reactor is adjusted to 8.0-8.5, and a sodium sulfide aqueous solution with a mass concentration of 10%-15% is added. The amount added is adjusted in real time according to the heavy metal concentration, that is, the molar ratio of cobalt and nickel ions to sodium sulfide is 1:1.2-1:1.5. The reaction time is 40-60 minutes.

[0034] In the step of adding sodium sulfide aqueous solution, nano-calcium carbonate seed crystals are also added simultaneously to promote the growth of sulfide precipitate particles, so that their particle size is ≥20μm and the sedimentation rate is increased to 0.3-0.5 m / h.

[0035] The nano-calcium carbonate seed crystals have a particle size of 50-100 nm and an addition amount of 50-100 mg / L.

[0036] After the reaction with added nano-calcium carbonate seeds is complete, the resulting suspension is introduced into a substrate with a surface loading of 0.8-1.0 m. 3 / (m 2 •h) An inclined tube sedimentation tank is used to remove heavy metal sulfide precipitates after solid-liquid separation. The precipitates are mainly CoS and NiS.

[0037] The step of adjusting the pH value of the wastewater after primary sedimentation is carried out in the fluoride removal reactor.

[0038] Among these measures, the pH value in the fluoride removal reactor is adjusted to 7.0-7.5.

[0039] The modified calcium chloride is modified with γ-aminopropyltriethoxysilane and has a specific surface area ≥50 m². 2 The modified calcium chloride is added at a concentration of 800-1500 mg / L, with a calcium-to-fluoride molar ratio of 1:1.8-1:2.0. The PAC dosage is 100-200 mg / L, and the reaction time is 60-90 minutes. This utilizes the enhanced adsorption capacity of the amino groups on the surface of the modified calcium chloride for fluoride ions, combined with the flocculation effect of PAC, to generate large-particle calcium fluoride precipitates (particle size ≥30μm). The precipitates can be removed by passing them through a high-efficiency filter (filtration accuracy 5μm).

[0040] In addition, chelating precipitants can be added to the wastewater after fluoride removal to achieve secondary heavy metal removal, remove residual trace heavy metal ions (such as lithium and manganese), and ensure that the heavy metal concentration is ≤0.1mg / L.

[0041] The chelating precipitant is, for example, sodium dithiocarbamate, with an addition amount of 50-100 mg / L, and the reaction pH is controlled at 7.5-8.0, with a reaction time of 30-40 minutes.

[0042] The process includes a step after the secondary heavy metal removal step: adding hydrochloric acid or sodium hydroxide to the wastewater after secondary precipitation to adjust the pH value to 7.0-8.0 for hydrolysis and acidification.

[0043] The hydrolysis and acidification step is carried out, for example, in a hydrolysis and acidification tank filled with modified biochar carriers, on which hydrolysis and acidification bacteria are attached. These hydrolysis and acidification bacteria include acid-producing bacteria and fermenting bacteria, and the inoculum size is 10. 6 -10 7 CFU / mL is used to decompose large organic molecules (such as NMP and dimethyl carbonate) into small organic molecules (such as acetic acid and propionic acid), thereby improving the biodegradability of wastewater (BOD5 / COD increases from 0.2-0.3 to 0.4-0.5).

[0044] The process includes, before the hydrolysis and acidification step, introducing the wastewater after secondary sedimentation into a biological conditioning tank, adding hydrochloric acid or sodium hydroxide to adjust the pH to 7.0-8.0, adding glucose as a co-metabolite substrate, and adding trace element nutrient solution to enhance microbial activity.

[0045] The glucose dosage is 10%-15% of COD, and the trace element nutrient solution contains Fe, Mn, Zn, Cu, etc., with a concentration of 5-10 mg / L.

[0046] The modified biochar carrier has a particle size of 10-20 mm and a specific surface area of ​​≥300 m². 2 / g.

[0047] The hydrolysis acidification tank has a hydraulic retention time of 8-12 hours, a temperature of 28-35℃, and a dissolved oxygen concentration of ≤0.5mg / L.

[0048] The wastewater from the hydrolysis acidification tank also enters the salt-tolerant aerobic aeration tank for segmented aeration treatment.

[0049] In the segmented aeration treatment step, the aeration intensity of the initial stage is 0.4-0.5 m. 3 / (m 2 •min), the aeration intensity in the later stage is 0.6-0.7 m 3 / (m 2 •min).

[0050] In the salt-tolerant aerobic aeration tank, a salt-tolerant composite microbial community was inoculated; the salt-tolerant composite microbial community consisted of Pseudomonas spp. ( Pseudomonas ), Bacillus spp. ( Bacillus Acinetobacter spp. Acinetobacter ), Rhodococcus ( Rhodococcus The inoculum is composed of ingredients in a mass ratio of 2:2:3:3, and the inoculum quantity is 10. 7 -10 8 CFU / mL.

[0051] Among them, the salt-tolerant composite microbial community has undergone gradient salinity acclimatization, with the salinity gradually increasing from 1% to 5%, and heavy metal tolerance acclimatization, with the heavy metal concentration gradually increasing from 5 mg / L to 20 mg / L, enabling it to efficiently degrade organic matter in a high-salt and high-toxicity environment.

[0052] The dissolved oxygen concentration in the salt-tolerant aerobic aeration tank is 2-4 mg / L, the hydraulic retention time is 16-24 hours, and the temperature is 28-35℃. Small molecule organic matter is decomposed into carbon dioxide and water through the aerobic metabolism of microorganisms.

[0053] The effluent from the salt-tolerant aerobic aeration tank is further introduced into a secondary sedimentation tank with a surface loading of 0.6-0.8 m³. 3 / (m 2 •h), the sedimentation time is 2-3 hours. In the secondary sedimentation tank, the microbial flocs are separated, the sludge return ratio is 50%-80%, and the remaining sludge is discharged into the sludge treatment system.

[0054] The effluent from the secondary sedimentation tank is also introduced into a catalytic ozone oxidation reactor. The catalytic ozone oxidation reactor is filled with a MnO2 / activated carbon composite catalyst. Ozone generates hydroxyl radicals (・OH) under the action of the MnO2 / activated carbon composite catalyst, which enhances the removal of residual recalcitrant organic matter (such as trace amounts of NMP), increasing the COD removal rate to over 90%, while also decolorizing and deodorizing.

[0055] In the catalytic ozone oxidation reactor, the MnO2 loading is 10%-15%, and the specific surface area is ≥200 m². 2 / g, ozone dosage is 80-150 mg / L, reaction time is 40-60 minutes, pH value is controlled at 7.5-8.5, and hydraulic retention time is 1.5-2 hours.

[0056] The wastewater after catalytic oxidation also enters an ultrafiltration membrane system and is filtered using a PVDF-modified ultrafiltration membrane.

[0057] The PVDF-modified ultrafiltration membrane has a pore size of 0.01-0.05 μm and a molecular weight cutoff of 5000-10000 Da. The ultrafiltration membrane system operates at a pressure of 0.15-0.3 MPa, a temperature of 20-35℃, and a transmembrane pressure difference controlled at 0.05-0.1 MPa.

[0058] The ultrafiltration membrane system is equipped with an online cleaning module, which adopts a combination of backwashing and chemical cleaning: backwashing is performed once every 30 minutes for 30 seconds; chemical cleaning uses citric acid with a mass concentration of 2%-3% and sodium hypochlorite with a mass concentration of 0.5%-1% alternately, once a week for 30-60 minutes each time, to extend the membrane life to 3-4 years.

[0059] The permeate from the ultrafiltration membrane system further enters the nanofiltration membrane system, where a fouling-resistant nanofiltration membrane is used for nanofiltration treatment to separate the salts in the water.

[0060] The fouling-resistant nanofiltration membrane has a molecular weight cutoff of 200-300 Da, the nanofiltration membrane system operates at a pressure of 0.8-1.2 MPa and a temperature of 25-30℃, and removes divalent salts (such as Ca) from the wastewater. 2+ SO4 2- ) and monovalent salts (such as Li) + Na + Separation is achieved, with a divalent salt rejection rate of ≥95% and a monovalent salt rejection rate of ≤30%, to avoid subsequent scaling of the reverse osmosis membrane.

[0061] The permeate from the nanofiltration membrane system also enters a two-stage reverse osmosis membrane system for reverse osmosis membrane treatment.

[0062] In the two-stage reverse osmosis membrane system, the first-stage reverse osmosis operates at a pressure of 1.2-1.5 MPa and a temperature of 25-30℃, with a desalination rate ≥99.5%; the first-stage permeate is used as primary recycled water with a conductivity ≤50μS / cm; the concentrate from the first-stage reverse osmosis enters the second-stage reverse osmosis system, operating at a pressure of 1.8-2.0 MPa with a desalination rate ≥99%; the second-stage reverse osmosis permeate is used as secondary recycled water with a conductivity ≤100μS / cm; and the concentrate from the second-stage reverse osmosis enters the concentrate treatment unit.

[0063] The concentrate from the second-stage reverse osmosis (salinity ≥10%) is then fed into the MVR evaporation and crystallization system for concentrate evaporation and crystallization treatment.

[0064] The MVR evaporation crystallization system has an evaporation temperature of 70-80℃ and a vacuum degree of -0.08~-0.09 MPa. The salts obtained by crystallization (such as NaCl and LiCl) are recycled after centrifugation, washing, and drying. As a result, the purity of NaCl is ≥98% and the purity of LiCl is ≥95%. The condensate is returned to the regulating tank for reprocessing.

[0065] The zero-discharge method for high-salt and high-complexity wastewater in the lithium battery industry also includes collecting the heavy metal sludge (primary sedimentation sludge), fluoride sludge (fluoride removal sludge) generated in the pretreatment stage and the biochemical sludge generated in the biochemical treatment stage separately to avoid cross-contamination.

[0066] The zero-discharge method for high-salt and high-complexity wastewater in the lithium battery industry also includes the step of feeding heavy metal sludge (70%-80% water content) into a sludge dryer for heavy metal sludge recovery.

[0067] In the heavy metal sludge recovery step, the drying temperature is 120-150℃, the drying time is 2-3 hours, and the moisture content of the dried sludge is ≤10%.

[0068] In the heavy metal sludge recovery step, the dried sludge is further fed into a roasting furnace for roasting at a temperature of 800-900℃ for 2-3 hours to remove organic matter and moisture, thereby obtaining a mixture of metal oxides (CoO and NiO content ≥30%).

[0069] The resulting metal oxide mixture is then added to an acid leaching tank, where 20%-30% sulfuric acid is added at a liquid-to-solid ratio of 5:1. The reaction temperature is 60-80℃, and the reaction time is 2-3 hours to dissolve the metal oxides. The solution is then filtered to obtain the leachate.

[0070] The leachate further enters a solvent extraction system, where cobalt and nickel ions are extracted using a 10%-15% P204 extractant with an extraction rate ≥95%. Back-extraction yields a cobalt and nickel enriched solution with a concentration ≥50 g / L, used to prepare a lithium-ion battery cathode material precursor. Lithium ions in the raffinate are recovered by adsorption using an ion exchange resin with an adsorption rate ≥90%, yielding Li... + Lithium salt solutions with a concentration ≥10g / L.

[0071] The fluoride sludge (70%-80% moisture content) is fed into a fluorine recovery reactor, where 98% sulfuric acid is added. The pH of the reaction is controlled at 1.0-2.0, and the reaction time is 60-90 minutes to generate hydrofluoric acid with a concentration of 10%-15%. Industrial-grade hydrofluoric acid (purity ≥99%) is obtained through distillation and purification and used in the production of lithium battery electrolytes. The reaction residue (mainly calcium sulfate) is washed and dried and used as a raw material for building materials.

[0072] The biochemical sludge is also processed in an anaerobic digester at a temperature of 35-38℃ and a hydraulic retention time of 20-25 days. The biogas produced (methane content ≥60%) is used to supplement the energy of the MVR evaporation crystallization system. The digested sludge is then concentrated and filtered (moisture content ≤60%) before being sent to a waste-to-energy plant for incineration. The waste heat from incineration is recovered and utilized.

[0073] This invention also proposes an integrated zero-discharge treatment system for high-salt, highly complex wastewater from the lithium battery industry, comprising: The equalization tank is used to contain wastewater generated during the lithium battery production process, and to regulate the water quality and quantity, so that the pH value of the wastewater is adjusted to 5.0-6.0 and the temperature is controlled at 25-30℃. The complex decomposition reactor is used to contain conditioned wastewater and to add a complex decomposition agent composed of ethylenediaminetetraacetic acid (such as disodium EDTA), sulfite and ferrous sulfate, so as to destroy the heavy metal-organic complex through redox and chelation competition, and release free heavy metal ions and organic matter. The primary sedimentation reactor is used to contain the wastewater after complex breaking and to add sulfide solution. The dosage is adjusted in real time according to the heavy metal concentration in order to remove heavy metal sulfide precipitates. The fluoride removal reactor is used to contain wastewater after primary sedimentation, adjust its pH to 7.0-7.5, and add modified calcium chloride and polyaluminum chloride to remove fluoride through precipitation.

[0074] The integrated zero-discharge treatment system for high-salt, complex wastewater from the lithium battery industry also includes: Online monitoring module: Online monitoring sensors are set up in each processing unit to monitor indicators such as pH, COD, BOD5, heavy metal concentration (Co, Ni, Li, Mn), fluoride concentration, salinity, conductivity, membrane flux, and transmembrane pressure difference in real time. The monitoring data is transmitted to the central control module in real time. The central control module, which adopts a PLC control system, automatically adjusts process parameters such as the dosage of reagents (e.g., complexing agents, sodium sulfide, modified calcium chloride, chelating agents, ozone), aeration intensity, stirring speed, membrane cleaning frequency, and evaporation crystallization temperature based on the monitoring data collected by the online monitoring module, thereby achieving automated and precise operation of the process.

[0075] The central control module is also equipped with a fault alarm function. When a certain indicator exceeds the standard or the equipment is abnormal, an alarm signal will be issued in a timely manner and an emergency handling procedure will be initiated.

[0076] This invention integrates an online monitoring module (real-time monitoring of multiple indicators) with a PLC control module to achieve real-time optimization of process parameters such as reagent dosage, aeration intensity, and membrane cleaning frequency, adapting to fluctuations in water quality and quantity.

[0077] The present invention also has the parameter linkage logic of the integrated processing system as described below: based on real-time monitoring data of indicators such as pH, COD, heavy metal concentration, and membrane flux, the system automatically adjusts indicators such as reagent dosage, aeration intensity, and membrane cleaning frequency.

[0078] The present invention also proposes a control algorithm to achieve the functions described above.

[0079] In a preferred embodiment, the present invention proposes a method for zero discharge of high-salt and highly complex wastewater from the lithium battery industry, comprising the following steps: 1. Preprocessing stage Equalization Tank: Wastewater generated during lithium battery production is collected in the equalization tank for water quality and quantity adjustment, stabilizing indicators such as pH (adjusted to 5.0-6.0), temperature (controlled at 25-30℃), and pollutant concentration. The equalization tank is equipped with a stirring device (stirring speed 60-80 r / min) and an online monitoring module (real-time monitoring of pH, COD, heavy metal concentration, and salinity) to ensure uniform mixing of the wastewater and provide real-time feedback of water quality data.

[0080] Complex Disintegration Unit: The adjusted wastewater is introduced into the complex disintegration reactor, and a composite complex-breaking agent (composed of disodium EDTA, sodium sulfite, and ferrous sulfate in a mass ratio of 3:2:1) is added at a dosage of 300-500 mg / L. The reaction pH is controlled at 2.5-3.5, the reaction time is 60-90 minutes, and the stirring speed is 40-50 r / min. Through redox and chelation competition, heavy metal-organic complexes (such as cobalt-NMP complexes) are destroyed, releasing free heavy metal ions and organic matter.

[0081] Primary heavy metal removal (sulfide staged precipitation): The dismantled wastewater is introduced into a primary precipitation reactor, the pH is adjusted to 8.0-8.5, and sodium sulfide solution (concentration 10%-15%) is added. The dosage is adjusted in real time according to the heavy metal concentration (molar ratio of cobalt and nickel ions to sodium sulfide is 1:1.2-1:1.5). The reaction time is 40-60 minutes. Simultaneously, nano-calcium carbonate seed crystals (particle size 50-100 nm, dosage 50-100 mg / L) are added to promote the growth of sulfide precipitate particles (particle size ≥20 μm), increasing the settling velocity to 0.3-0.5 m / h. After the reaction, the wastewater enters an inclined tube sedimentation tank (surface loading 0.8-1.0 m). 3 / (m 2 •h)), after solid-liquid separation, heavy metal sulfide precipitates (mainly CoS and NiS) are removed.

[0082] Fluoride removal (modified calcium salt precipitation): The wastewater after primary precipitation is introduced into the fluoride removal reactor, the pH is adjusted to 7.0-7.5, and modified calcium chloride (modified by γ-aminopropyltriethoxysilane, with a specific surface area ≥50 m²) is added. 2 The modified calcium chloride (calcium chloride) and polyaluminum chloride (PAC) were added at a dosage of 800-1500 mg / L (calcium-fluoride molar ratio 1:1.8-1:2.0), and the PAC dosage was 100-200 mg / L. The reaction time was 60-90 minutes. The amino groups on the surface of the modified calcium chloride enhanced its adsorption capacity for fluoride ions. Combined with the flocculation effect of PAC, large-particle calcium fluoride precipitates (particle size ≥30μm) were generated, which were then removed by a high-efficiency filter (filtration accuracy 5μm).

[0083] Secondary heavy metal removal (chelation precipitation): The wastewater after fluoride removal is introduced into a secondary precipitation reactor, and a chelating precipitant (sodium dithiocarbamate) is added at a dosage of 50-100 mg / L. The reaction pH is controlled at 7.5-8.0, and the reaction time is 30-40 minutes to remove residual trace heavy metal ions (such as lithium and manganese) and ensure that the heavy metal concentration is ≤0.1 mg / L.

[0084] 2. Enhanced biochemical treatment stage (additional salt tolerance acclimatization and carrier fixation) Pretreatment: The wastewater after secondary sedimentation is introduced into the biological conditioning tank, and hydrochloric acid or sodium hydroxide is added to adjust the pH value to 7.0-8.0. Glucose (10%-15% of COD) is added as a co-metabolite substrate, and trace element nutrient solution (containing Fe, Mn, Zn, Cu, etc., at a concentration of 5-10 mg / L) is added at the same time to enhance the activity of microorganisms.

[0085] Hydrolysis acidification tank (carrier-enhanced): The conditioned wastewater is introduced into the hydrolysis acidification tank, which is filled with modified biochar carrier (particle size 10-20 mm, specific surface area ≥300 m²). 2 / g), hydraulic retention time of 8-12 hours, temperature of 28-35℃, dissolved oxygen concentration ≤0.5 mg / L. Modified biochar carrier adsorbs organic matter and provides attachment sites for hydrolytic acidifying bacteria (including acid-producing bacteria and fermenting bacteria, inoculated at a density of 10...). 6 -10 7 CFU / mL decomposes large organic molecules (such as NMP and dimethyl carbonate) into small organic molecules (such as acetic acid and propionic acid), improving the biodegradability of wastewater (BOD5 / COD increases from 0.2-0.3 to 0.4-0.5).

[0086] Salt-tolerant aerobic aeration tank (stratified microbial culture): Wastewater enters the salt-tolerant aerobic aeration tank from the hydrolysis acidification tank. The tank adopts a segmented aeration design (initial aeration intensity 0.4-0.5 m). 3 / (m 2 •min), the latter part is 0.6-0.7 m 3 / (m 2 •min), inoculate with a salt-tolerant complex microbial community (composed of Pseudomonas, Bacillus, Acinetobacter, and Rhodococcus in a mass ratio of 2:2:3:3), with an inoculation amount of 10 7 -10 8CFU / mL. This bacterial community, after undergoing gradient salinity acclimation (salinity gradually increased from 1% to 5%) and heavy metal tolerance acclimation (heavy metal concentration gradually increased from 5 mg / L to 20 mg / L), can efficiently degrade organic matter in a high-salt, highly toxic environment. By controlling the dissolved oxygen concentration in the aerobic aeration tank to 2-4 mg / L, the hydraulic retention time to 16-24 hours, and the temperature to 28-35℃, the microorganisms decompose small-molecule organic matter into carbon dioxide and water through aerobic metabolism.

[0087] Secondary sedimentation tank: The effluent from the aerobic aeration tank is introduced into the secondary sedimentation tank, with a surface loading of 0.6-0.8 m³. 3 / (m 2 • h), the settling time is 2-3 hours, the microbial flocs are separated, the sludge return ratio is 50%-80%, and the remaining sludge is discharged into the sludge treatment system.

[0088] 3. Deep processing stage Catalytic ozone oxidation: The effluent from the secondary sedimentation tank is introduced into the catalytic ozone oxidation reactor, which is filled with a MnO2 / activated carbon composite catalyst (MnO2 loading of 10%-15%, specific surface area ≥200 m²). 2 The ozone dosage is 80-150 mg / L, the reaction time is 40-60 minutes, the pH value is controlled at 7.5-8.5, and the hydraulic retention time is 1.5-2 hours. Ozone generates hydroxyl radicals (・OH) under the action of a catalyst, enhancing the removal of residual recalcitrant organic matter (such as trace amounts of NMP), increasing the COD removal rate to over 90%, while also decolorizing and deodorizing.

[0089] Ultrafiltration membrane filtration (modified membrane + online cleaning): The wastewater after catalytic oxidation enters the ultrafiltration membrane system, using a PVDF modified ultrafiltration membrane (pore size 0.01-0.05μm, molecular weight cutoff 5000-10000Da). The operating pressure is 0.15-0.3 MPa, the temperature is 20-35℃, and the transmembrane pressure difference is controlled at 0.05-0.1 MPa. The system is equipped with an online cleaning module, using a combination of backwashing and chemical cleaning: backwashing is performed every 30 minutes for 30 seconds; chemical cleaning uses alternating cleaning with citric acid (concentration 2%-3%) and sodium hypochlorite (concentration 0.5%-1%), once a week for 30-60 minutes each time, extending the membrane life to 3-4 years.

[0090] Nanofiltration desalination: Ultrafiltration permeate enters the nanofiltration membrane system, using a fouling-resistant nanofiltration membrane (molecular weight cutoff 200-300 Da). The operating pressure is 0.8-1.2 MPa, and the temperature is 25-30℃. This process removes divalent salts (such as Ca2+) from the wastewater. 2+ SO4 2- ) and monovalent salts (such as Li) + Na +Separation is achieved, with a divalent salt rejection rate of ≥95% and a monovalent salt rejection rate of ≤30%, to avoid subsequent scaling of the reverse osmosis membrane.

[0091] Reverse osmosis membrane treatment (two-stage): Nanofiltration permeate enters the two-stage reverse osmosis membrane system. The first-stage reverse osmosis system operates at a pressure of 1.2-1.5 MPa and a temperature of 25-30℃, with a desalination rate ≥99.5%. The permeate is used as primary recycled water (conductivity ≤50μS / cm). The first-stage concentrate enters the second-stage reverse osmosis system, operating at a pressure of 1.8-2.0 MPa, with a desalination rate ≥99%. The permeate is used as secondary recycled water (conductivity ≤100μS / cm). The second-stage concentrate enters the concentrate treatment unit.

[0092] Concentrate evaporation and crystallization: The second-stage reverse osmosis concentrate (salinity ≥10%) enters the MVR evaporation and crystallization system. The evaporation temperature is 70-80℃ and the vacuum degree is -0.08~-0.09 MPa. The crystallized salts (such as NaCl and LiCl) are centrifuged, washed, and dried for recycling (NaCl purity ≥98%, LiCl purity ≥95%). The condensate is returned to the equalization tank for reprocessing.

[0093] 4. Solid waste resource utilization stage Sludge collection and classification: Heavy metal sludge (primary sedimentation sludge), fluoride sludge (fluoride removal sludge) generated in the pretreatment stage and biochemical sludge generated in the biochemical treatment stage are collected separately to avoid cross-contamination.

[0094] Heavy metal sludge recovery: Heavy metal sludge (moisture content 70%-80%) enters a sludge dryer (drying temperature 120-150℃, drying time 2-3 hours). After drying, the sludge moisture content is ≤10%, and then it is sent to a roasting furnace (roasting temperature 800-900℃, roasting time 2-3 hours) to remove organic matter and moisture, obtaining a metal oxide mixture (CoO, NiO content ≥30%). The metal oxide mixture is added to an acid leaching tank, sulfuric acid (concentration 20%-30%) is added, the liquid-to-solid ratio is 5:1, the reaction temperature is 60-80℃, and the reaction time is 2-3 hours to dissolve the metal oxides. The solution is then filtered to obtain the leachate. The leachate enters a solvent extraction system, where cobalt and nickel ions are extracted using P204 extractant (concentration 10%-15%), achieving an extraction rate ≥95%. Back-extraction yields a cobalt and nickel enriched solution (concentration ≥50 g / L), used to prepare a lithium-ion battery cathode material precursor. Lithium ions in the raffinate are recovered by adsorption using an ion exchange resin (adsorption rate ≥90%) to obtain a lithium salt solution (Li). + Concentration ≥10g / L).

[0095] Fluoride sludge recovery: Fluoride sludge (70%-80% moisture content) enters the fluoride recovery reactor, sulfuric acid (98% concentration) is added, the reaction pH is controlled at 1.0-2.0, and the reaction time is 60-90 minutes to generate hydrofluoric acid (10%-15% concentration). Industrial-grade hydrofluoric acid (≥99% purity) is obtained through distillation and purification, and used in the production of lithium battery electrolytes. The reaction residue (mainly calcium sulfate) is washed and dried and used as a raw material for building materials.

[0096] Biochemical sludge treatment: Biochemical sludge enters the anaerobic digester, where the digestion temperature is 35-38℃ and the hydraulic retention time is 20-25 days. The biogas produced (methane content ≥60%) is used to supplement the energy of the MVR evaporation crystallization system. The digested sludge is concentrated and filtered (moisture content ≤60%) and then sent to the waste incineration power plant for incineration treatment, and the waste heat from incineration is recovered and utilized.

[0097] 5. Intelligent control system Online monitoring module: Online monitoring sensors are set up in each processing unit to monitor indicators such as pH, COD, BOD5, heavy metal concentration (Co, Ni, Li, Mn), fluoride concentration, salinity, conductivity, membrane flux, and transmembrane pressure difference in real time. The monitoring data is transmitted to the central control system in real time.

[0098] Central Control System: Employing a PLC control system, this system automatically adjusts process parameters such as reagent dosage (e.g., complexing agents, sodium sulfide, modified calcium chloride, chelating agents, ozone), aeration intensity, stirring speed, membrane cleaning frequency, and evaporation / crystallization temperature based on monitoring data, achieving automated and precise process operation. It also includes a fault alarm function; when any indicator exceeds the limit or equipment malfunctions, an alarm signal is promptly issued and emergency response procedures are initiated.

[0099] The present invention will be further illustrated below through specific embodiments. It should be noted that the following embodiments are merely illustrative and not intended to limit the present invention.

[0100] Example 1: Treatment of mixed wastewater with high salinity and high COD Wastewater source: Mixed wastewater from a lithium battery manufacturing company (positive electrode material + negative electrode coating + electrolyte wastewater), with the following water quality indicators: pH 5.5, COD 2500 mg / L, salinity 4.5%, heavy metal cobalt ion concentration 80 mg / L, nickel ion concentration 40 mg / L, lithium ion concentration 120 mg / L, fluoride concentration 200 mg / L, containing cobalt-NMP complex (concentration 50 mg / L), SS 600 mg / L.

[0101] Processing steps Preprocessing stage : Equalization tank: Wastewater is introduced into the equalization tank, the pH is adjusted to 5.5, the stirring speed is 70 r / min, and the retention time is 2 hours. COD 2500 mg / L, salinity 4.5%, and heavy metal concentration are monitored online.

[0102] Complex disintegration: Introduce a disintegration reactor, add a composite complex breaker (disodium EDTA + sodium sulfite + ferrous sulfate = 3:2:1), add 400 mg / L, pH 3.0, react for 70 minutes, stir at 45 r / min, and disintegrate the cobalt-NMP complex.

[0103] Primary heavy metal removal: The sample enters the primary precipitation reactor, where the pH is adjusted to 8.2. A 12% sodium sulfide solution is added (dosage: 1000 mg / L, cobalt, nickel, and sodium sulfide molar ratio: 1:1.3), followed by the addition of 80 mg / L of nano-calcium carbonate seed crystals. The reaction is carried out for 50 minutes, and the sample then enters an inclined tube sedimentation tank (surface loading 0.9 m). 3 / (m 2 • h)) ), precipitation for 1 hour to remove CoS and NiS precipitates.

[0104] Fluoride removal: The mixture is introduced into a fluoride removal reactor, the pH is adjusted to 7.2, and modified calcium chloride 1200 mg / L (calcium-fluoride molar ratio 1:1.9) and PAC 150 mg / L are added. The reaction is carried out for 70 minutes, and the calcium fluoride precipitate is removed by a high-efficiency filter (5 μm precision).

[0105] Secondary heavy metal removal: The sample enters a secondary precipitation reactor, where sodium dithiocarbamate (80 mg / L) is added at pH 7.8. The reaction is carried out for 35 minutes to remove residual lithium and manganese ions.

[0106] Enhanced biochemical treatment stage : Biochemical conditioning tank: Adjust pH to 7.5, add glucose 300mg / L (12% of COD), trace element nutrient solution 8mg / L, and retain for 1 hour.

[0107] Hydrolysis acidification tank: filled with modified biochar carrier, hydraulic retention time of 10 hours, temperature of 32℃, dissolved oxygen of 0.3mg / L, BOD5 / COD increased from 0.25 to 0.45.

[0108] Salt-tolerant aerobic aeration tank: segmented aeration (first stage 0.45 m) 3 / (m 2 •min), the latter part is 0.65m 3 / (m 2 •min), inoculated with a salt-tolerant complex microbial community (Pseudomonas: Bacillus: Acinetobacter: Rhodococcus = 2:2:3:3), inoculation amount 108 CFU / mL, dissolved oxygen 3 mg / L, hydraulic retention time 20 hours, temperature 32℃.

[0109] Secondary sedimentation tank: surface loading 0.7m 3 / (m 2 • h), sedimentation for 2.5 hours, sludge return ratio 60%.

[0110] Deep processing stage : Catalytic ozone oxidation: filled with MnO2 / activated carbon composite catalyst, ozone dosage 120 mg / L, pH 8.0, reaction time 50 minutes, hydraulic retention time 1.8 hours.

[0111] Ultrafiltration membrane filtration: PVDF modified ultrafiltration membrane (pore size 0.03μm), operating pressure 0.2 MPa, temperature 28℃, transmembrane pressure difference 0.08 MPa, online cleaning (backwashing 30 minutes / time, chemical cleaning once a week).

[0112] Nanofiltration for salt separation: Fouling-resistant nanofiltration membrane, operating pressure 1.0 MPa, temperature 28℃, divalent salt rejection rate 96%.

[0113] Two-stage reverse osmosis: the first stage operates at a pressure of 1.3 MPa and a temperature of 28°C; the second stage operates at a pressure of 1.9 MPa and a temperature of 28°C.

[0114] Concentrated water evaporation crystallization: MVR evaporation temperature 75℃, vacuum degree -0.085 MPa, recovering NaCl (purity 98.5%) and LiCl (purity 95.2%).

[0115] Solid waste resource utilization stage: Heavy metal sludge: drying temperature 130℃, calcination temperature 850℃, sulfuric acid leaching (concentration 25%), P204 extraction of cobalt and nickel (extraction rate 95.5%), and lithium recovery by ion exchange (adsorption rate 91%).

[0116] Fluoride sludge: Add 98% sulfuric acid, pH 1.5, react for 70 minutes, and recover hydrofluoric acid (purity 99.2%).

[0117] Biochemical sludge: Anaerobic digestion (temperature 37℃, retention time 22 days), biogas is used to supplement MVR energy, and digested sludge is incinerated after filter pressing (moisture content 58%).

[0118] Treatment results: The primary recycled water quality indicators are pH 7.2, COD 28 mg / L, conductivity 42 μS / cm, cobalt ions 0.03 mg / L, nickel ions 0.02 mg / L, lithium ions 0.04 mg / L, and fluoride 2.5 mg / L; the secondary recycled water has a COD of 35 mg / L and a conductivity of 85 μS / cm, both meeting the recycling requirements of each process in lithium battery production; the water reuse rate is 96%, and the solid waste recycling value is 62 yuan / ton of wastewater.

[0119] Example 2: Wastewater Treatment for High-Fluoride and High-Heavy-Metal Cathode Materials Wastewater source: Wastewater from the production of cathode materials (ternary materials) of a lithium battery manufacturing company. The water quality indicators are: pH value 2.0, COD 1800 mg / L, salinity 2.5%, heavy metal cobalt ion concentration 150 mg / L, nickel ion concentration 60 mg / L, manganese ion concentration 30 mg / L, lithium ion concentration 100 mg / L, fluoride concentration 250 mg / L, containing nickel-ethylene glycol complex (concentration 40 mg / L), SS 400 mg / L.

[0120] Processing steps Preprocessing stage : Conditioning tank: Adjust pH to 5.0, stir at 65 r / min, retain for 2.5 hours, and monitor all indicators online.

[0121] Complex disintegration: Add 350 mg / L of composite complex breaker, pH 3.2, react for 65 minutes, stir at 40 r / min to disintegrate nickel-ethylene glycol complex.

[0122] Primary heavy metal removal: Adjust pH to 8.3, add 1200 mg / L of 15% sodium sulfide solution (molar ratio 1:1.4), 90 mg / L of nano-calcium carbonate seed crystals, react for 55 minutes, and then settle in an inclined tube sedimentation tank for 1.2 hours.

[0123] Fluoride removal: Adjust pH to 7.3, add 1400 mg / L modified calcium chloride (calcium-fluoride molar ratio 1:2.0) and 180 mg / L PAC, react for 80 minutes, and remove the precipitate using a high-efficiency filter.

[0124] Secondary heavy metal removal: Add sodium dithiocarbamate 90 mg / L, pH 7.9, and react for 40 minutes.

[0125] Enhanced biochemical treatment stage : Biochemical conditioning tank: Adjust pH to 7.3, add glucose 270mg / L (15% of COD), trace element nutrient solution 7mg / L, and retain for 1.5 hours.

[0126] Hydrolysis acidification tank: hydraulic retention time 11 hours, temperature 33℃, BOD5 / COD increased to 0.48.

[0127] Salt-tolerant aerobic aeration tank: segmented aeration (0.4 m3 / (m2・min) in the first stage and 0.7 m3 / (m2・min) in the second stage), inoculated with salt-tolerant compound microbial community, inoculation amount 108 CFU / mL, dissolved oxygen 3.5 mg / L, hydraulic retention time 22 hours, temperature 33℃.

[0128] Secondary sedimentation tank: surface loading rate 0.65 m3 / (m2・h), sedimentation time 3 hours, sludge return ratio 70%.

[0129] Deep processing stage : Catalytic ozone oxidation: ozone dosage 130 mg / L, pH 8.2, reaction time 55 minutes, hydraulic retention time 2 hours.

[0130] Ultrafiltration membrane filtration: operating pressure 0.25MPa, temperature 30℃, transmembrane pressure difference 0.09MPa.

[0131] Nanofiltration salt separation: operating pressure 1.1 MPa, temperature 30℃, divalent salt rejection rate 97%.

[0132] Two-stage reverse osmosis: first stage pressure 1.4MPa, second stage pressure 2.0MPa.

[0133] Concentrated water evaporation and crystallization: recovery of NaCl (purity 98.3%) and LiCl (purity 95.5%).

[0134] Solid waste resource utilization stage : Heavy metal sludge: drying temperature 140℃, calcination temperature 880℃, sulfuric acid leaching (concentration 28%), P204 extraction of cobalt, nickel and manganese (extraction rate 96%), and lithium recovery by ion exchange (adsorption rate 92%).

[0135] Fluoride sludge: recover hydrofluoric acid (99.3% purity).

[0136] Biochemical sludge: after anaerobic digestion, it is incinerated and biogas is recovered and utilized.

[0137] Treatment results: Primary recycled water has a pH of 7.1, COD of 25 mg / L, conductivity of 38 μS / cm, cobalt ions of 0.02 mg / L, nickel ions of 0.01 mg / L, manganese ions of 0.02 mg / L, lithium ions of 0.03 mg / L, and fluoride of 2.2 mg / L; Secondary recycled water has a COD of 32 mg / L and conductivity of 78 μS / cm; Water reuse rate is 95.5%, and the solid waste recycling value is 75 yuan / ton of wastewater.

[0138] Example 3: Wastewater Treatment of High NMP and High Salt Anode Coating Wastewater source: Wastewater from negative electrode coating of a lithium battery manufacturing enterprise. Water quality indicators are: pH 7.0, COD 3000 mg / L, salinity 3.5%, lithium ion concentration 80 mg / L, fluoride concentration 150 mg / L, NMP concentration 1200 mg / L, SS 800 mg / L, and salinity 3.5%.

[0139] Processing steps The overall steps are the same as in Example 2, except that the following steps differ: Complex disintegration: Add 500 mg / L of complex cleavage agent, pH 2.8, and react for 90 minutes (for high NMP).

[0140] Primary heavy metal removal: Sodium sulfide dosage 800 mg / L, pH 8.1, reaction time 60 minutes.

[0141] Fluoride removal: 1000 mg / L modified calcium chloride, 200 mg / L PAC, reaction time 90 minutes.

[0142] Enhanced biochemical treatment: hydraulic retention time in the hydrolysis acidification tank is 12 hours, hydraulic retention time in the aerobic aeration tank is 24 hours, and microbial inoculation amount is 108 CFU / mL (enhanced NMP degradation).

[0143] Catalytic ozone oxidation: ozone dosage 150 mg / L, reaction time 60 minutes (deep removal of residual NMP).

[0144] Solid waste recycling: lithium recovery from heavy metal sludge (adsorption rate 93%), hydrofluoric acid recovery from fluoride sludge (purity 99.1%).

[0145] Treatment results: The primary recycled water had a COD of 26 mg / L, a conductivity of 45 μS / cm, a lithium ion concentration of 0.03 mg / L, and a fluoride concentration of 2.8 mg / L; the water reuse rate was 96.2%, the NMP removal rate was 99.8%, and the solid waste recycling value was 58 yuan / ton of wastewater.

[0146] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for zero discharge of high-salt, highly complex wastewater from the lithium battery industry, characterized in that, Includes the following steps: Wastewater generated during lithium battery production is collected in an equalization tank to adjust the water quality and quantity, thereby adjusting the pH value of the wastewater to 5.0-6.0 and controlling the temperature at 25-30℃. Adding a complex complex-breaking agent composed of ethylenediaminetetraacetate, sulfite and ferrous sulfate to the adjusted wastewater breaks down heavy metal-organic complexes through redox and chelation competition, releasing free heavy metal ions and organic matter. Sulfide solution is added to the wastewater after the complex is broken up. The amount added is adjusted in real time according to the heavy metal concentration to remove heavy metal sulfide precipitates. After primary sedimentation, the pH of the wastewater is adjusted to 7.0-7.5, and modified calcium chloride and polyaluminum chloride are added to remove fluoride through precipitation.

2. The method for zero discharge of high-salt, high-complexity wastewater from the lithium battery industry according to claim 1, characterized in that, The step of collecting wastewater into the equalization tank also includes installing a stirring device and an online monitoring module within the equalization tank; wherein the stirring speed is 60-80 r / min; the online monitoring module monitors pH, COD, heavy metal concentration, and salinity in real time to ensure uniform mixing of the wastewater; and / or The step of adding a composite complex-breaking agent to the regulated wastewater is carried out in a complex disintegration reactor; the composite complex-breaking agent is composed of disodium ethylenediaminetetraacetate, sodium sulfite, and ferrous sulfate in a mass ratio of 3:2:1; the dosage of the composite complex-breaking agent is 300-500 mg / L, the reaction pH is controlled at 2.5-3.5, the reaction time is 60-90 minutes, and the stirring speed is 40-50 r / min; and / or The step of adding sulfide solution to the complex-broken wastewater is carried out in a primary precipitation reactor; the pH of the primary precipitation reactor is adjusted to 8.0-8.5, and a sodium sulfide aqueous solution with a mass concentration of 10%-15% is added. The dosage is adjusted in real time according to the heavy metal concentration, i.e., the molar ratio of cobalt and nickel ions to sodium sulfide is 1:1.2-1:1.5, and the reaction time is 40-60 minutes; and / or A chelating precipitant is added to the wastewater after fluoride removal to achieve secondary heavy metal removal, remove residual trace heavy metal ions, and ensure that the heavy metal concentration is ≤0.1mg / L.

3. The method for zero discharge of high-salt and highly complex wastewater from the lithium battery industry according to claim 2, characterized in that, In the step of adding sodium sulfide aqueous solution, nano-calcium carbonate seed crystals are also added simultaneously to promote the growth of sulfide precipitate particles, so that their particle size is ≥20μm and the sedimentation rate is increased to 0.3-0.5 m / h; The step of adjusting the pH value of the wastewater after primary sedimentation is carried out in the fluoride removal reactor; the pH value in the fluoride removal reactor is adjusted to 7.0-7.5; When modified calcium chloride is added, the modified calcium chloride is modified with γ-aminopropyltriethoxysilane and has a specific surface area ≥50 m². 2 / g, the dosage of modified calcium chloride is 800-1500 mg / L, the calcium-fluorine molar ratio is 1:1.8-1:2.0, the dosage of PAC is 100-200 mg / L, and the reaction time is 60-90 minutes; When adding modified calcium chloride, the process also includes the step of using the amino groups on the surface of modified calcium chloride to enhance the adsorption capacity for fluoride ions, combined with the flocculation effect of PAC, to generate large-particle calcium fluoride precipitates with a particle size ≥30μm, and then removing the precipitates through a high-efficiency filter with a filtration accuracy of 5μm. When adding a chelating precipitant to the wastewater after fluoride removal, the chelating precipitant is sodium dithiocarbamate, the dosage is 50-100 mg / L, the reaction pH is controlled at 7.5-8.0, and the reaction time is 30-40 minutes. Following the secondary heavy metal removal step, the process also includes adding hydrochloric acid or sodium hydroxide to the wastewater after secondary precipitation to adjust the pH value to 7.0-8.0 for hydrolysis and acidification.

4. The method for zero discharge of high-salt and high-complexity wastewater from the lithium battery industry according to claim 3, characterized in that, The particle size of the nano-calcium carbonate seed crystals is 50-100 nm, and the dosage is 50-100 mg / L; After the reaction with nano-calcium carbonate seeds is complete, the resulting suspension is introduced into a solution with a surface loading of 0.8-1.0 m. 3 / (m 2 •h) Inclined tube sedimentation tank, after solid-liquid separation, removes heavy metal sulfide precipitates; The hydrolysis acidification step is carried out in a hydrolysis acidification tank filled with modified biochar carriers, on which hydrolysis acidification bacteria are attached. The hydrolysis acidification bacteria include acid-producing bacteria and fermenting bacteria, with an inoculation amount of 106-107 CFU / mL, which are used to decompose large molecular organic matter into small molecular organic matter and improve the biodegradability of wastewater. Before the hydrolysis and acidification step, the process includes introducing the wastewater after secondary sedimentation into a biological conditioning tank, adding hydrochloric acid or sodium hydroxide to adjust the pH to 7.0-8.0, adding glucose as a co-metabolite substrate, and adding a trace element nutrient solution to enhance microbial activity. The glucose dosage is 10%-15% of the COD, and the trace element nutrient solution contains Fe, Mn, Zn, and Cu at a concentration of 5-10 mg / L. The modified biochar carrier has a particle size of 10-20 mm and a specific surface area ≥300 m². 2 / g; The hydraulic retention time in the hydrolysis acidification tank is 8-12 hours, the temperature is 28-35℃, and the dissolved oxygen concentration is ≤0.5mg / L.

5. The method for zero discharge of high-salt, high-complexity wastewater from the lithium battery industry according to claim 1, characterized in that, The wastewater from the hydrolysis acidification tank then enters the salt-tolerant aerobic aeration tank for segmented aeration treatment.

6. The method for zero discharge of high-salt and highly complex wastewater from the lithium battery industry according to claim 5, characterized in that, In the segmented aeration treatment step, the aeration intensity of the initial stage is 0.4-0.5 m. 3 / (m 2 •min), the aeration intensity in the later stage is 0.6-0.7 m 3 / (m 2 •min); The salt-tolerant aerobic aeration tank was inoculated with a salt-tolerant composite microbial community; the salt-tolerant composite microbial community consisted of Pseudomonas spp. ( Pseudomonas ), Bacillus spp. Bacillus Acinetobacter spp. Acinetobacter ), Rhodococcus ( Rhodococcus The inoculum is composed of ingredients in a mass ratio of 2:2:3:3, and the inoculum quantity is 10. 7 -10 8 CFU / mL; The salt-tolerant composite microbial community, after being subjected to gradient salinity acclimatization (salt level gradually increased from 1% to 5%) and heavy metal tolerance acclimatization (heavy metal concentration gradually increased from 5 mg / L to 20 mg / L), is able to efficiently degrade organic matter in a high-salt and high-toxicity environment. The dissolved oxygen concentration in the salt-tolerant aerobic aeration tank is 2-4 mg / L, the hydraulic retention time is 16-24 hours, and the temperature is 28-35℃. Small molecule organic matter is decomposed into carbon dioxide and water through the aerobic metabolism of microorganisms. The effluent from the salt-tolerant aerobic aeration tank is also introduced into a secondary sedimentation tank, with a surface loading of 0.6-0.8 m³. 3 / (m 2 •h), the settling time is 2-3 hours. In the secondary settling tank, the microbial flocs are separated, the sludge return ratio is 50%-80%, and the remaining sludge is discharged into the sludge treatment system. The effluent from the secondary sedimentation tank is also introduced into a catalytic ozone oxidation reactor, which is filled with a MnO2 / activated carbon composite catalyst. Under the action of the MnO2 / activated carbon composite catalyst, ozone generates hydroxyl radicals, which enhances the removal of residual recalcitrant organic matter and increases the COD removal rate to over 90%, while also decolorizing and deodorizing. In the catalytic ozone oxidation reactor, the MnO2 loading is 10%-15%, and the specific surface area is ≥200 m². 2 / g, ozone dosage is 80-150 mg / L, reaction time is 40-60 minutes, pH value is controlled at 7.5-8.5, and hydraulic retention time is 1.5-2 hours.

7. The method for zero discharge of high-salt and highly complex wastewater from the lithium battery industry according to claim 1, characterized in that, The wastewater after catalytic oxidation also enters an ultrafiltration membrane system for filtration treatment using a PVDF-modified ultrafiltration membrane; and / or The permeate from the ultrafiltration membrane system further enters the nanofiltration membrane system, where a fouling-resistant nanofiltration membrane is used for nanofiltration treatment to separate salts from the water; and / or The permeate from the nanofiltration membrane system also enters a two-stage reverse osmosis membrane system for reverse osmosis membrane treatment; and / or The concentrate from the second-stage reverse osmosis also enters the MVR evaporation and crystallization system for concentrate evaporation and crystallization treatment; and / or The zero-discharge method for high-salt and complex wastewater in the lithium battery industry also includes collecting the heavy metal sludge, fluoride sludge generated in the pretreatment stage and the biochemical sludge generated in the biochemical treatment stage separately to avoid cross-contamination. and / or The method for zero discharge of high-salt and complex wastewater from the lithium battery industry also includes the step of feeding heavy metal sludge into a sludge dryer for heavy metal sludge recovery.

8. The method for zero discharge of high-salt and high-complexity wastewater from the lithium battery industry according to claim 7, characterized in that, When an ultrafiltration membrane system is used for processing, the PVDF-modified ultrafiltration membrane has a pore size of 0.01-0.05 μm, a molecular weight cutoff of 5000-10000 Da, an operating pressure of 0.15-0.3 MPa, a temperature of 20-35℃, and a transmembrane pressure difference controlled at 0.05-0.1 MPa. When using an ultrafiltration membrane system for processing, the ultrafiltration membrane system is equipped with an online cleaning module, which adopts a combination of "backwashing + chemical cleaning": the backwashing frequency is once every 30 minutes, and the backwashing time is 30 seconds; the chemical cleaning uses citric acid with a mass concentration of 2%-3% and sodium hypochlorite with a mass concentration of 0.5%-1% alternately, once a week, for 30-60 minutes each time, to extend the membrane life to 3-4 years; When using a fouling-resistant nanofiltration membrane for nanofiltration treatment, the fouling-resistant nanofiltration membrane has a molecular weight cutoff of 200-300 Da, the operating pressure of the nanofiltration membrane system is 0.8-1.2 MPa, and the temperature is 25-30℃. It separates divalent salts from monovalent salts in wastewater, with a divalent salt rejection rate of ≥95% and a monovalent salt rejection rate of ≤30%, thus avoiding scaling of the subsequent reverse osmosis membrane. When a two-stage reverse osmosis membrane system is used for treatment, the operating pressure of the first stage reverse osmosis is 1.2-1.5 MPa, the temperature is 25-30℃, and the desalination rate is ≥99.5%; the permeate from the first stage is used as primary recycled water with a conductivity ≤50μS / cm; the concentrate from the first stage reverse osmosis enters the second stage reverse osmosis, with an operating pressure of 1.8-2.0 MPa and a desalination rate ≥99%; the permeate from the second stage reverse osmosis is used as secondary recycled water with a conductivity ≤100μS / cm; the concentrate from the second stage reverse osmosis enters the concentrate treatment unit. When the MVR evaporation crystallization system is used for processing, the evaporation temperature of the MVR evaporation crystallization system is 70-80℃, the vacuum degree is -0.08~-0.09 MPa, and the salts obtained by crystallization are recycled after centrifugation, washing and drying. As a result, the purity of NaCl is ≥98% and the purity of LiCl is ≥95%. The condensate is returned to the equalization tank for reprocessing. When the process includes a heavy metal sludge recycling step, the drying temperature in the heavy metal sludge recycling step is 120-150℃, the drying time is 2-3 hours, and the moisture content of the dried sludge is ≤10%. When the heavy metal sludge undergoes a drying process, the dried sludge is then fed into a roasting furnace for roasting at a temperature of 800-900℃ for 2-3 hours to remove organic matter and moisture, thereby obtaining a mixture of metal oxides. When heavy metal sludge is roasted to obtain a metal oxide mixture, the metal oxide mixture is added to an acid leaching tank, and sulfuric acid with a concentration of 20%-30% is added. The liquid-solid ratio is 5:1, the reaction temperature is 60-80℃, the reaction time is 2-3 hours, the metal oxides are dissolved, and the leachate is obtained by filtration. When heavy metal sludge is added to an acid leaching tank to obtain a leachate, the leachate also enters a solvent extraction system. Cobalt and nickel ions are extracted using a 10%-15% concentration of P204 extractant, with an extraction rate ≥95%. Back-extraction yields a cobalt and nickel enriched solution with a concentration ≥50 g / L, which is used to prepare lithium-ion battery cathode material precursors. Lithium ions in the raffinate are recovered by adsorption using an ion exchange resin, with an adsorption rate ≥90%, to obtain Li... + Lithium salt solutions with a concentration ≥10 g / L; When the process includes a fluoride sludge recovery treatment step, the fluoride sludge also enters a fluoride recovery reactor, where 98% sulfuric acid is added. The reaction pH is controlled at 1.0-2.0, and the reaction time is 60-90 minutes, generating 10%-15% hydrofluoric acid. This hydrofluoric acid is purified by distillation to obtain industrial-grade hydrofluoric acid, which is used in the production of lithium battery electrolytes. The reaction residue is washed and dried and then used as a raw material for building materials. When the biochemical sludge recycling and treatment step is included, the biochemical sludge also enters the anaerobic digester for treatment. The digestion temperature is 35-38℃ and the hydraulic retention time is 20-25 days. The biogas produced is used to supplement the energy of the MVR evaporation crystallization system. After digestion, the sludge is concentrated and filtered, and then sent to the waste incineration power plant for incineration treatment. The waste heat from incineration is recovered and utilized.

9. An integrated zero-discharge treatment system for high-salt, highly complex wastewater from the lithium battery industry, characterized in that, include: The equalization tank is used to contain wastewater generated during the lithium battery production process, and to regulate the water quality and quantity, so that the pH value of the wastewater is adjusted to 5.0-6.0 and the temperature is controlled at 25-30℃. The complex decomposition reactor is used to contain the conditioned wastewater and to add a composite complex decomposing agent composed of ethylenediaminetetraacetate, sulfite and ferrous sulfate, so as to destroy the heavy metal-organic complex through redox and chelation competition, and release free heavy metal ions and organic matter. The primary sedimentation reactor is used to contain the wastewater after complex breaking and to add sulfide solution. The dosage is adjusted in real time according to the heavy metal concentration in order to remove heavy metal sulfide precipitates. The fluoride removal reactor is used to contain wastewater after primary sedimentation, adjust its pH to 7.0-7.5, and add modified calcium chloride and polyaluminum chloride to remove fluoride through precipitation.

10. The method for zero discharge of high-salt, high-complexity wastewater from the lithium battery industry according to claim 9, characterized in that, in, The integrated zero-discharge treatment system for high-salt and complex wastewater from the lithium battery industry also includes: Online monitoring module: Online monitoring sensors are set up in each processing unit to monitor indicators such as pH, COD, BOD5, heavy metal concentration, fluoride concentration, salinity, conductivity, membrane flux, and transmembrane pressure difference in real time. The monitoring data is transmitted to the central control module in real time. The central control module, which adopts a PLC control system, automatically adjusts process parameters such as reagent dosage, aeration intensity, stirring speed, membrane cleaning frequency, and evaporation crystallization temperature based on monitoring data collected by the online monitoring module, thereby achieving automated and precise operation of the process.

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