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CN-122010347-A - High-salt high-complexity wastewater zero discharge method and integrated treatment system in lithium battery industry

CN122010347ACN 122010347 ACN122010347 ACN 122010347ACN-122010347-A

Abstract

A zero discharge method and an integrated treatment system for high-salt and high-complexity wastewater in the lithium battery industry relate to the field of wastewater treatment. The zero discharge method of the wastewater comprises the steps of collecting the lithium battery wastewater into an adjusting tank for water quality and water quantity adjustment, adding a composite decomplexing agent consisting of ethylenediamine tetraacetate, sulfite and ferrous sulfate into the adjusted wastewater, destroying heavy metal-organic complex through the competition of oxidation reduction and chelation, adding sulfide solution into the decomplexing wastewater for removing heavy metal sulfide precipitation, adjusting the pH value of the wastewater after primary precipitation to 7.0-7.5, adding modified calcium chloride and polyaluminium chloride into the wastewater, and removing fluoride through precipitation. The invention realizes the deep removal of various pollutants through the synergistic effect of complex disassembly, fractional precipitation, enhanced biochemistry, catalytic oxidation and membrane separation, wherein the removal rate of heavy metal ions can reach more than 99.9%, and the removal rate of organic matters COD can reach more than 95%.

Inventors

  • ZHANG YOUDE
  • LI ZHIMENG
  • ZHOU LIANG

Assignees

  • 赛科斯智能装备(合肥)有限公司

Dates

Publication Date
20260512
Application Date
20260317

Claims (10)

  1. 1. The zero-emission method for the high-salt high-complexity wastewater in the lithium battery industry is characterized by comprising the following steps of: collecting the wastewater generated in the lithium battery production process into an adjusting tank, adjusting the water quality and the water quantity to adjust the pH value of the wastewater to 5.0-6.0, and controlling the temperature to 25-30 ℃; Adding a composite decomplexing agent consisting of ethylenediamine tetraacetate, sulfite and ferrous sulfate into the regulated wastewater, and destroying heavy metal-organic matter complexes through the competition of oxidation reduction and chelation to release free heavy metal ions and organic matters; Adding sulfide solution into the waste water after the vein breaking, and adjusting the adding amount in real time according to the concentration of heavy metal to remove heavy metal sulfide precipitate; and regulating the pH value of the wastewater after the primary precipitation to 7.0-7.5, adding modified calcium chloride and polyaluminum chloride into the wastewater, and removing fluoride through precipitation.
  2. 2. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 1, wherein, The method comprises the steps of collecting wastewater into an adjusting tank, arranging a stirring device and an online monitoring module in the adjusting 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 the composite vein breaker into the regulated wastewater is carried out in a complex dismantling reactor, the composite vein breaker consists of disodium ethylenediamine tetraacetate, sodium sulfite and ferrous sulfate according to the mass ratio of 3:2:1, the adding amount of the composite vein breaker is 300-500 mg/L, the reaction pH value is controlled to be 2.5-3.5, the reaction time is 60-90 minutes, the stirring rotation speed is 40-50r/min, and/or the reaction time is controlled to be less than or equal to the total mass ratio of the disodium ethylenediamine tetraacetate, the sodium sulfite and the ferrous sulfate The step of adding sulfide solution into the waste water after the vein breaking is carried out in a primary precipitation reactor, the pH value of the primary precipitation reactor is regulated to 8.0-8.5, sodium sulfide aqueous solution with the mass concentration of 10-15% is added, the adding amount is regulated in real time according to the heavy metal concentration, namely, the molar ratio of cobalt, nickel ions and sodium sulfide is 1:1.2-1:1.5, the reaction time is 40-60 minutes, and/or And adding a chelating precipitant into the wastewater after fluoride removal to remove secondary heavy metals and residual trace heavy metal ions, wherein the concentration of the heavy metals is ensured to be less than or equal to 0.1mg/L.
  3. 3. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 2, wherein, In the step of adding the sodium sulfide aqueous solution, nano calcium carbonate seed crystals are also added at the same time to promote the growth of sulfide precipitation particles, so that the particle size of the sulfide precipitation particles is more than or equal to 20 mu m, and the sedimentation speed is increased to 0.3-0.5 m/h; the step of adjusting the pH value of the wastewater after the primary precipitation is carried out in a fluoride removal reactor, wherein the pH value in the fluoride removal reactor is adjusted to 7.0-7.5; when the modified calcium chloride is added, the modified calcium chloride is modified by gamma-aminopropyl triethoxysilane, the specific surface area is more than or equal to 50 m 2 /g, the adding amount of the modified calcium chloride is 800-1500 mg/L, the molar ratio of calcium to fluorine is 1:1.8-1:2.0, the adding amount of PAC is 100-200 mg/L, and the reaction time is 60-90 minutes; when the modified calcium chloride is added, the method further comprises the steps of utilizing amino groups on the surface of the modified calcium chloride to enhance the adsorption capacity to fluoride ions, combining the flocculation of PAC to generate large-particle calcium fluoride precipitates with the particle size of more than or equal to 30 mu m, and removing the precipitates through a high-efficiency filter with the filtering precision of 5 mu m; When a chelating precipitant is added into the wastewater after fluoride removal, wherein the chelating precipitant is sodium dithiocarbamate, the adding amount is 50-100mg/L, the pH value of the reaction is controlled to be 7.5-8.0, and the reaction time is 30-40 minutes; after the secondary heavy metal removal step, the method also comprises the step of adding hydrochloric acid or sodium hydroxide into the wastewater after the secondary precipitation to adjust the pH value to 7.0-8.0, and carrying out hydrolysis acidification.
  4. 4. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 3, wherein, The grain diameter of the nano calcium carbonate seed crystal is 50-100 nm, and the adding amount is 50-100 mg/L; After the reaction of adding nano calcium carbonate seed crystal is finished, the generated suspension enters a inclined tube sedimentation tank with the surface load of 0.8-1.0 m 3 /(m 2 seed h), and heavy metal sulfide sediment is removed after solid-liquid separation; the hydrolysis acidification step is carried out in a hydrolysis acidification tank, a modified biochar carrier is filled in the hydrolysis acidification tank, hydrolysis acidification bacteria are attached to the hydrolysis acidification tank, the hydrolysis acidification bacteria comprise acidogenic bacteria and zymophyte, the inoculation amount is 106-107 CFU/mL, and the hydrolysis acidification tank is used for decomposing macromolecular organic matters into micromolecular organic matters and improving the biodegradability of wastewater; Before the step of hydrolysis acidification, the method further comprises the step of introducing the wastewater after secondary precipitation into a biochemical regulating tank, adding hydrochloric acid or sodium hydroxide to regulate the pH value to 7.0-8.0, adding glucose as a co-metabolism substrate, and adding a trace element nutrient solution to improve the microbial activity, wherein the adding amount of the glucose is 10% -15% of COD, the trace element nutrient solution comprises Fe, mn, zn, cu-10 mg/L of concentration, the particle size of the modified biochar carrier is 10-20 mm, and the specific surface area is more than or equal to 300 m 2 /g; The hydraulic retention time of the hydrolysis acidification tank is 8-12 hours, the temperature is 28-35 ℃, and the concentration of dissolved oxygen is less than or equal to 0.5mg/L.
  5. 5. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 1, wherein the wastewater from the hydrolysis acidification tank also enters a salt-tolerant aerobic aeration tank for segmented aeration treatment.
  6. 6. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 5, wherein, In the step of segmented aeration treatment, the aeration intensity of the front segment is 0.4-0.5 m 3 /(m 2 seed min, and the aeration intensity of the rear segment is 0.6-0.7 m 3 /(m 2 seed min); Inoculating a salt-tolerant composite microbial flora in the salt-tolerant aerobic aeration tank, wherein the salt-tolerant composite microbial flora consists of Pseudomonas (Pseudomonas), bacillus (Bacillus), acinetobacter (Acinetobacter) and Rhodococcus (Rhodococcus) in a mass ratio of 2:2:3:3, and the inoculation amount is 10 7 -10 8 CFU/mL; The salt-tolerant compound microbial flora is subjected to gradient salinity domestication, the salinity is gradually increased from 1% to 5%, and the heavy metal tolerance domestication, the heavy metal concentration is gradually increased from 5 mg/L to 20 mg/L, so that organic matters can be efficiently degraded in a high-salt and high-toxicity environment; The dissolved oxygen concentration of the salt-tolerant aerobic aeration tank is 2-4 mg/L, the hydraulic retention time is 16-24 hours, the temperature is 28-35 ℃, and micromolecular organic matters are decomposed into carbon dioxide and water through aerobic metabolism of microorganisms; The effluent of the salt-tolerant aerobic aeration tank is also introduced into a secondary sedimentation tank, the surface load is 0.6-0.8m 3 /(m 2 (a seed h), the sedimentation time is 2-3 hours, in the secondary sedimentation tank, microbial flocs are separated, the sludge reflux ratio is 50-80%, and the residual sludge is discharged into a sludge treatment system; The effluent of the secondary sedimentation tank is also introduced into a catalytic ozonation reactor, mnO 2 /activated carbon composite catalyst is filled in the catalytic ozonation reactor, ozone generates hydroxyl free radicals under the action of the MnO 2 /activated carbon composite catalyst, the removal of residual refractory organic matters is enhanced, the COD removal rate is increased to more than 90%, and meanwhile, the waste water is decolorized and deodorized; in the catalytic ozonation reactor, the MnO 2 load is 10% -15%, the specific surface area is not less than 200 m 2 /g, the ozone adding amount 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.
  7. 7. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 1, wherein, The wastewater after catalytic oxidation also enters an ultrafiltration membrane system, and is subjected to filtration treatment by adopting a PVDF modified ultrafiltration membrane, and/or The produced water of the ultrafiltration membrane system further enters a nanofiltration membrane system, and is subjected to nanofiltration treatment by adopting a pollution-resistant nanofiltration membrane to separate the salt in the water, and/or The produced water of the nanofiltration membrane system also enters a two-stage reverse osmosis membrane system to carry out reverse osmosis membrane treatment and/or The concentrated water of the two-stage reverse osmosis also enters an MVR evaporative crystallization system to carry out concentrated water evaporative crystallization treatment and/or The zero discharge method of the high-salt high-complexity wastewater in the lithium battery industry further comprises the steps of respectively collecting heavy metal sludge, fluoride sludge and biochemical sludge generated in the pretreatment stage and the biochemical treatment stage, avoiding cross contamination, and/or The high-salt high-complexity wastewater zero-emission method in the lithium battery industry further comprises the step of conveying the heavy metal sludge into a sludge dryer for heavy metal sludge recovery.
  8. 8. The method for zero discharge of high-salt and high-complexity wastewater in the lithium battery industry according to claim 7, wherein, When an ultrafiltration membrane system is adopted for treatment, the aperture of the PVDF modified ultrafiltration membrane is 0.01-0.05 mu m, the molecular weight cut-off is 5000-10000 Da, the operating pressure of the ultrafiltration membrane system is 0.15-0.3 MPa, the temperature is 20-35 ℃, and the transmembrane pressure difference is controlled to be 0.05-0.1MPa; When the ultrafiltration membrane system is adopted for treatment, the ultrafiltration membrane system is provided with an online cleaning module, a combined mode of 'backwashing and chemical cleaning' is adopted, wherein the backwashing frequency is 1 time every 30 minutes, the backwashing time is 30 seconds, the chemical cleaning adopts 2-3% of citric acid and 0.5-1% of sodium hypochlorite for alternating cleaning, the frequency is 1 time every week, 30-60 minutes each time, and the service life of the membrane is prolonged to 3-4 years; When the pollution-resistant nanofiltration membrane is adopted for nanofiltration treatment, the molecular weight cut-off of the pollution-resistant nanofiltration membrane is 200-300 Da, the operating pressure of a nanofiltration membrane system is 0.8-1.2-MPa, the temperature is 25-30 ℃, divalent salt and monovalent salt in wastewater are separated, the divalent salt cut-off rate is more than or equal to 95%, the monovalent salt cut-off rate is less than or equal to 30%, and the subsequent reverse osmosis membrane scaling is avoided; When the two-stage reverse osmosis membrane system is adopted for treatment, the operation pressure of the first-stage reverse osmosis membrane system is 1.2-1.5 MPa, the temperature is 25-30 ℃, the desalination rate is more than or equal to 99.5%, the first-stage produced water is used as first-stage reuse water, the conductivity is less than or equal to 50 mu S/cm, the first-stage reverse osmosis concentrated water enters the second-stage reverse osmosis system, the operation pressure is 1.8-2.0 MPa, the desalination rate is more than or equal to 99%, the second-stage reverse osmosis produced water is used as second-stage reuse water, the conductivity is less than or equal to 100 mu S/cm, and the second-stage reverse osmosis concentrated water enters the concentrated water treatment unit; When the MVR evaporative crystallization system is adopted for treatment, the evaporation temperature of the MVR evaporative crystallization system is 70-80 ℃, the vacuum degree is-0.08 to-0.09 MPa, and salts obtained by crystallization are centrifugally separated, washed and dried and then recycled, so that the purity of NaCl is more than or equal to 98%, the purity of LiCl is more than or equal to 95%, and condensed water returns to an adjusting tank for reprocessing; When the method comprises a heavy metal sludge recovery treatment step, in the heavy metal sludge recovery step, the drying temperature is 120-150 ℃, the drying time is 2-3 hours, and the water content of the dried sludge is less than or equal to 10%; When the heavy metal sludge is subjected to a drying treatment step, the dried sludge is further sent into a roasting furnace for roasting, the roasting temperature is 800-900 ℃, the roasting time is 2-3 hours, and organic matters and water are removed to obtain a metal oxide mixture; when the heavy metal sludge is roasted to obtain a metal oxide mixture, the obtained metal oxide mixture is also added into an acid leaching tank, sulfuric acid with the 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 oxide is dissolved, and the leaching solution is obtained by filtering; When heavy metal sludge is added into an acid leaching tank to obtain leaching liquid, the leaching liquid also enters a solvent extraction system, a P204 extractant with the concentration of 10% -15% is adopted to extract cobalt and nickel ions, the extraction rate is more than or equal to 95%, and a cobalt and nickel enrichment solution with the concentration of more than or equal to 50g/L is obtained through back extraction and is used for preparing a precursor of a lithium battery anode material; when the method comprises the fluoride sludge recovery treatment step, the fluoride sludge also enters a fluoride recovery reactor, sulfuric acid with the concentration of 98% is added, the pH value of the reaction is controlled to be 1.0-2.0, the reaction time is controlled to be 60-90 minutes, hydrofluoric acid with the concentration of 10% -15% is generated, and the industrial grade hydrofluoric acid is obtained through distillation and purification and is used for producing lithium battery electrolyte; When the method comprises the steps of biochemical sludge recovery treatment, biochemical sludge is treated in an anaerobic digestion tank at the digestion temperature of 35-38 ℃ for 20-25 days, the generated biogas is used for supplementing energy of an MVR evaporation crystallization system, and the digested sludge is subjected to concentration and pressure filtration and is sent to a garbage incineration power plant for incineration treatment, and the incineration waste heat is recycled.
  9. 9. High salt high complexity waste water zero release integrated processing system of lithium cell trade, characterized in that includes: The regulating tank is used for accommodating wastewater generated in the lithium battery production process, regulating the water quality and the water quantity, regulating the pH value of the wastewater to 5.0-6.0 and controlling the temperature to 25-30 ℃; the complex disassembly reactor is used for accommodating the regulated wastewater, and adding a composite decomplexing agent consisting of ethylenediamine tetraacetate, sulfite and ferrous sulfate so as to destroy heavy metal-organic matter complexes and release free heavy metal ions and organic matters through the competing action of redox and chelation; the first-stage precipitation reactor is used for containing the wastewater after the vein breaking and throwing sulfide solution, and the throwing amount is adjusted in real time according to the concentration of heavy metal so as to remove heavy metal sulfide precipitate; A fluoride removal reactor for accommodating wastewater after the primary precipitation, adjusting the pH thereof to 7.0-7.5, and charging modified calcium chloride and polyaluminum chloride thereto to remove fluoride by precipitation.
  10. 10. The method for zero discharge of high-salt, high-complexity wastewater in the lithium battery industry of claim 9, wherein the integrated treatment system for zero discharge of high-salt, high-complexity wastewater in the lithium battery industry further comprises: The on-line monitoring module is used for setting on-line monitoring sensors in each processing unit, monitoring pH, COD, BOD, heavy metal concentration, fluoride concentration, salinity, conductivity, membrane flux, transmembrane pressure difference and other indexes in real time, and transmitting monitoring data to the central control module in real time; And the central control module adopts a PLC control system, automatically adjusts technological parameters such as the dosage of the medicament, the aeration intensity, the stirring rotating speed, the membrane cleaning frequency, the evaporation crystallization temperature and the like based on the monitoring data acquired by the on-line monitoring module, and realizes the automatic and accurate operation of the process.

Description

High-salt high-complexity wastewater zero discharge method and integrated treatment system in lithium battery industry Technical Field The invention relates to the technical field of wastewater treatment, in particular to a high-salt high-complexity wastewater zero-discharge method and an integrated treatment system in the lithium battery industry. Background With the transition of global energy structures to low carbonization, lithium batteries are used as core components of electric automobiles and energy storage systems, and the market scale is expanded in an explosive manner. According to the data of white paper of 2024 global lithium battery industry, the output of 2023 global lithium batteries reaches 1525GWh, which is increased by 35% in a same way, wherein the output of Chinese lithium batteries accounts for more than 70% of the world. In the production process of the lithium battery, a large amount of waste water is generated in the working procedures of preparation of a positive electrode material (such as ternary material and lithium iron phosphate), coating of a negative electrode, preparation of electrolyte, cleaning of the battery and the like, and according to the measurement, about 500-800 tons of waste water is generated per 1GWh of lithium battery production. Heavy metal ions (such as cobalt and nickel) in the lithium battery wastewater have biological enrichment, long-term accumulation can cause damage to liver and kidney functions of a human body, fluoride can cause calcification of soil and damage to plant roots, plant death can be directly caused when the concentration exceeds 50mg/L, and organic pollutant NMP has reproductive toxicity and threatens the health of the human body through a food chain. According to the report of water pollution discharge in the important industry in 2023 of the ecological environment department, the exceeding standard rate of fluoride in the wastewater discharge in the lithium battery industry reaches 28%, the comprehensive standard rate of heavy metal is only 72%, and the standard rate of high-salt wastewater treatment is less than 60%. Meanwhile, the environmental protection policy is becoming strict, china ' water pollution control program (' Water Ten ') clearly requires the key industry to realize zero wastewater discharge before 2025 years, european Union ' Industrial discharge Command (IED) prescribes that fluoride discharge of lithium battery production wastewater is limited to 10mg/L, total discharge concentration of heavy metals is not more than 0.1mg/L, domestic industry standard ' Water pollutant discharge Standard (request opinion) of lithium battery industry aims to set COD limit in the quality of recycled water to be less than 50mg/L, conductivity is less than or equal to 100 mu S/cm, fluoride is less than or equal to 5mg/L, and heavy metal single factor is less than or equal to 0.05mg/L. Such wastewater also has significant complexity and extremes: (1) The contaminants are multiple and interact. Contains heavy metal ions such as cobalt, nickel, lithium, manganese and the like (the concentration is usually 10-200 mg/L), fluoride (50-300 mg/L), organic pollutants (COD can reach 1000-3000mg/L, mainly N-methylpyrrolidone (NMP), glycol, dimethyl carbonate and the like), and part of heavy metals and organic matters form stable complexes (such as cobalt-NMP complex) which are difficult to disassemble by a conventional method; (2) The water quality has extremely strong fluctuation. The water quality difference of the waste water in different working procedures is extremely large, the waste water of the positive electrode material is strong acid (pH is less than or equal to 2) and rich in fluoride, the coating waste water of the negative electrode contains high-concentration NMP and suspended matters (SS is more than or equal to 500 mg/L), and the salt content of the waste water of the electrolyte exceeds 5 percent (mainly LiPF 6 and NaCl), so that the traditional single treatment process is difficult to stably run; (3) High salt and high toxicity synergistic inhibition. The synergistic effect of salinity (0.5% -5%) in the wastewater and heavy metals and fluorides further aggravates the treatment difficulty, and the conventional biochemical system is hardly tolerant. The current lithium battery wastewater treatment technology is mainly divided into a single treatment method and a combined treatment method, but has obvious limitations: 1. Chemical treatment method The neutralization precipitation method is to adjust the pH to be alkaline (8-11) by adding NaOH and Ca (OH) 2, so that heavy metal ions form hydroxide precipitates. The method has the cobalt and nickel removal rate of 85-90 percent, but has four defects: ① The fluoride removal effect is poor (only 30% -50%), and excessive calcium salt (the molar ratio of calcium to fluorine is more than or equal to 2:1) needs to be additionally added, so that the sludge yield is increased by more than 30%