Multi-barrier coupled treatment process for organic complex heavy metals in battery cathode material production wastewater

Abstract

A multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from battery cathode material production is disclosed, relating to the field of wastewater treatment. The method involves: 1. Adjusting the pH of the wastewater to 3.0-4.5; 2. Adding iron salt and peracetic acid to an oxidation reaction tank; 3. Achieving primary removal of heavy metals through neutralization and precipitation after oxidation; 4. Adjusting the pH of the wastewater back to 6.0-6.5; 5. Passing the wastewater sequentially through a primary adsorption unit and a secondary adsorption unit. This invention utilizes the low bond energy characteristics of PAA and the synergistic oxidation advantages of multiple free radicals to solve the bottleneck problems of incomplete complex breaking, large sludge production, and narrow pH application range in traditional methods. After treatment by this invention, the total nickel concentration in the effluent is less than 0.05 mg / L, and the total cobalt concentration is less than 0.02 mg / L, consistently exceeding the limits of the "Emission Standard of Pollutants for Battery Industry" (GB 30484-2013), demonstrating broad industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of wastewater, specifically to a multi-barrier coupling treatment process for organic complexed heavy metals in wastewater from the production of battery cathode materials. Background Technology

[0002] In recent years, with the profound transformation of the global energy structure, the lithium-ion battery industry has entered a stage of explosive growth. Currently, the mainstream cathode materials for commercial lithium-ion power batteries include ternary materials (LiNi). x Co y Mn z Lithium oxide (NCO), lithium iron phosphate (LFP), lithium manganese oxide (LMO), and lithium cobalt oxide (LCO) are among the various types of lithium batteries. NCO dominates the lithium battery market due to its high energy density and long cycle life. However, the synthesis, electroplating, cleaning, and wet recycling of spent batteries generate large amounts of complex industrial wastewater. This wastewater not only contains high concentrations of heavy metal ions such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li), but also contains a large amount of organic complexing agents artificially added to improve production process performance.

[0003] Common organic complexing agents in battery wastewater include ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (NTA), citric acid, tartaric acid, and various phosphonates. These complexing agents contain abundant electron-donating groups such as hydroxyl, carboxyl, and amino groups, readily forming stable chelates with polycyclic structures through coordination with transition metal ions. This complexing significantly alters the chemical form of heavy metal ions in water, allowing them to remain highly soluble over a wide pH range (even under strongly alkaline conditions), whereas previously they could be precipitated as hydroxides by adjusting pH. These organically complexed heavy metals (HMCs) exhibit higher biotoxicity and environmental mobility than free metals. They mask the electrical properties of metal ions, weakening their adsorption efficiency on soil minerals and biofilm surfaces, thereby accelerating the penetration of heavy metals into deep groundwater and the top of the food chain, causing irreversible environmental damage.

[0004] For organically complexed heavy metals in this type of wastewater, existing chemical precipitation methods are limited by the extremely high stability constants of metal chelates, making conventional hydroxide precipitation difficult, while sulfide precipitation faces limitations such as fine sludge and secondary pollution; the traditional Fenton oxidation process (Fe... 2+The optimal pH range for H2O2 is extremely narrow (usually 2.5~3.5), resulting in high reagent consumption and the generation of large amounts of iron-containing hazardous sludge, which increases the disposal burden. Ion exchange and membrane separation technologies are easily affected by organic additives when treating such high-concentration and complex wastewater, leading to resin poisoning and inactivation or membrane module blockage and damage. In addition, the system cost and operation and maintenance costs are high, making it difficult to meet the dual requirements of treatment efficiency and economy for large-scale industrial applications.

[0005] To address the aforementioned bottlenecks, there is an urgent need to develop an efficient, broad-spectrum, and environmentally friendly complex-breaking and deep purification process to treat this type of wastewater. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of low removal rate of organic complex heavy metals, large dosage of pH adjustment agents and high production of iron-containing hazardous sludge in existing battery wastewater treatment technologies, and to provide a multi-barrier coupling treatment process for organic complex heavy metals in battery cathode material production wastewater.

[0007] This invention aims to develop a coupled treatment process of "PAA complex breaking + neutralization precipitation + deep adsorption". Through a multi-barrier coupling mechanism, it can achieve green, energy-saving and efficient removal of organic complexed heavy metals in wastewater from battery cathode material production, and ensure that the effluent quality meets the standards stably.

[0008] A multi-barrier coupling treatment process for organic complexed heavy metals in wastewater from battery cathode material production is specifically carried out according to the following steps:

[0009] 1. The wastewater generated from battery production or recycling is fed into an equalization tank, where the water quantity and quality are homogenized. The pH value of the wastewater is then adjusted to 3.0-4.5 to obtain pH-adjusted wastewater.

[0010] 2. The pH-adjusted wastewater is pumped into the oxidation reaction tank, and FeSO4·7H2O solution and peracetic acid solution are added. The reaction is carried out under stirring conditions for a period of time. The generated ·OH and organic free radicals synergistically break the metal-organic complex bond to obtain the effluent from the oxidation reaction tank.

[0011] 3. The effluent from the oxidation reaction tank enters the inclined tube sedimentation tank, and then NaOH solution is added to adjust the pH value of the wastewater to 10.0~10.5. Then, coagulant and coagulant aid are added in sequence to complete physical sedimentation. The generated sludge is sent to the sludge treatment system, and the supernatant enters the intermediate water tank.

[0012] 4. Add dilute hydrochloric acid to the intermediate water tank to adjust the pH value of the wastewater back to 6.0~6.5, thus obtaining wastewater with a pH value of 6.0~6.5;

[0013] 5. The wastewater with a pH value of 6.0~6.5 is pumped into the deep adsorption system and flows through the primary adsorption unit and the secondary adsorption unit in sequence to obtain the wastewater treated by the deep adsorption system.

[0014] VI. Wastewater treated by the deep adsorption system meets the relevant industry emission standards or reuse standards, achieving compliant discharge or reuse in production processes.

[0015] The principles and advantages of this invention:

[0016] I. This invention discloses a multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from battery cathode material production. First, the battery wastewater enters a regulating tank for pretreatment. The water quantity and quality are homogenized using a stirring or aeration device at the bottom of the regulating tank, and the pH value of the wastewater is pre-adjusted to 3.0-4.5 using an automatic dosing system to provide a stable physicochemical matrix for the subsequent oxidation reaction. Second, the effluent from the regulating tank enters an oxidation reaction tank, where an iron salt catalyst (FeSO4·7H2O) and a PAA oxidant are added. The system utilizes hydroxyl radicals (·OH) and acetoxy radicals (·CH3) generated in situ within the system. The synergistic effect of reactive oxygen species (ROS) such as C(O)O and acetylperoxy radicals (·CH3C(O)OO) directionally disrupts the metal-ligand chelate structure, achieving organic ligand degradation and the release of heavy metal ions. Among them, ·OH has an extremely high oxidation potential, enabling non-selective and powerful oxidation, while organic free radicals exhibit higher anti-interference selectivity and a longer half-life, jointly ensuring the thoroughness of complex disruption in complex water quality conditions. Then, the oxidized effluent enters the inclined tube sedimentation tank for neutralization and flocculation separation. The in-situ co-precipitation effect of iron salts achieves primary removal of heavy metals, and the settled sludge is discharged into the sludge treatment system. Next, the supernatant after sedimentation enters the intermediate tank for pH adjustment. Subsequently, the wastewater enters the deep adsorption system, passing through the primary adsorption unit and the secondary adsorption unit in sequence, utilizing the gradient barrier mechanism to achieve complete retention of residual trace heavy metals.

[0017] Second, compared with traditional methods, the present invention has a simplified process flow, a wider applicable pH range, and can significantly reduce the amount of sludge generated.

[0018] Third, this invention utilizes the low bond energy characteristics of PAA and the synergistic oxidation advantages of multiple free radicals to solve the bottleneck problems of incomplete complex breaking, large sludge production, and narrow pH application range of traditional methods. After treatment by the process of this invention, the total nickel concentration in the effluent is less than 0.05 mg / L and the total cobalt concentration is less than 0.02 mg / L, which is consistently better than the limits of the "Emission Standard of Pollutants for Battery Industry" (GB 30484-2013), and has broad prospects for industrial application. Detailed Implementation

[0019] Specific Implementation Method 1: This implementation method is a multi-barrier coupling treatment process for organic complexed heavy metals in wastewater from battery cathode material production, specifically carried out according to the following steps:

[0020] 1. The wastewater generated from battery production or recycling is fed into an equalization tank, where the water quantity and quality are homogenized. The pH value of the wastewater is then adjusted to 3.0-4.5 to obtain pH-adjusted wastewater.

[0021] 2. The pH-adjusted wastewater is pumped into the oxidation reaction tank, and FeSO4·7H2O solution and peracetic acid solution are added. The reaction is carried out under stirring conditions for a period of time. The generated ·OH and organic free radicals synergistically break the metal-organic complex bond to obtain the effluent from the oxidation reaction tank.

[0022] 3. The effluent from the oxidation reaction tank enters the inclined tube sedimentation tank, and then NaOH solution is added to adjust the pH value of the wastewater to 10.0~10.5. Then, coagulant and coagulant aid are added in sequence to complete physical sedimentation. The generated sludge is sent to the sludge treatment system, and the supernatant enters the intermediate water tank.

[0023] 4. Add dilute hydrochloric acid to the intermediate water tank to adjust the pH value of the wastewater back to 6.0~6.5, thus obtaining wastewater with a pH value of 6.0~6.5;

[0024] 5. The wastewater with a pH value of 6.0~6.5 is pumped into the deep adsorption system and flows through the primary adsorption unit and the secondary adsorption unit in sequence to obtain the wastewater treated by the deep adsorption system.

[0025] VI. Wastewater treated by the deep adsorption system meets the relevant industry emission standards or reuse standards, achieving compliant discharge or reuse in production processes.

[0026] In step two of this embodiment, the hydroxyl radicals generated in situ in the system work synergistically with highly selective organic radicals to directionally destroy the metal-ligand chelate structure and release heavy metal ions.

[0027] In step three of this embodiment, the initial removal of heavy metals is achieved through neutralization precipitation (pH 10.0~10.5) after oxidation;

[0028] In step four of this embodiment, the pH of the clarified liquid is adjusted to 6.0-6.5 before entering the deep adsorption system;

[0029] In step five of this embodiment, the residual trace heavy metals are completely intercepted by passing through an activated carbon interception barrier and a special chelating resin capture barrier in sequence.

[0030] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: in step one, the pH value of the wastewater is adjusted to 3.0-4.5 using sulfuric acid or hydrochloric acid with a mass fraction of 10%-30%; and in step one, the water quantity and quality are homogenized using a stirring device or aeration device installed at the bottom of the equalization tank. Other steps are the same as in Specific Implementation Method One.

[0031] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the total nickel concentration in the wastewater described in step one is 10 mg / L to 500 mg / L, the total cobalt concentration is 5 mg / L to 200 mg / L, and the COD concentration is 200 mg / L to 1500 mg / L. The other steps are the same as in Specific Implementation Method One or Two.

[0032] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the reaction time in step two is 45 min to 90 min; the mass fraction of the peracetic acid solution in step two is 15% to 20%. Other steps are the same as in Specific Implementation Methods One to Three.

[0033] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the mass fraction of the FeSO4·7H2O solution mentioned in step two is 10%; the dosage of the FeSO4·7H2O solution mentioned in step two is 0.1 g / L to 5 g / L. The other steps are the same as in Specific Implementation Methods One to Four.

[0034] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Methods One through Five is that the Fe added in step two... 2+ The molar ratio of the substance to peracetic acid is 1:(1~5). Other steps are the same as in specific embodiments one to five.

[0035] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the mass fraction of the NaOH solution mentioned in step three is 30%; the coagulant mentioned in step three is polyaluminum chloride; and the coagulant aid mentioned in step three is polyacrylamide. Other steps are the same as in Specific Implementation Methods One to Six.

[0036] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the dosage of the coagulant in step three is 100 mg / L to 300 mg / L, and the dosage of the coagulant aid is 2 mg / L to 5 mg / L; the hydraulic retention time of the inclined tube sedimentation tank in step three is 1.5 h to 2.5 h. Other steps are the same as in Specific Implementation Methods One to Seven.

[0037] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the mass fraction of the dilute hydrochloric acid mentioned in step four is 5%; the primary adsorption unit mentioned in step five is filled with activated carbon to physically intercept suspended solids and quench residual oxidants, protecting the subsequent resin; the secondary adsorption unit mentioned in step five is filled with iminodiacetic acid-type chelating resin to capture residual trace metal ions. Other steps are the same as in Specific Implementation Methods One to Eight.

[0038] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the iminodiacetic acid type chelating resin is model D402, purchased from Jiangsu Suqing Water Treatment Engineering Group Co., Ltd.; the empty bed velocity of the primary adsorption unit and the secondary adsorption unit in step five is 2~10 BV / h. Other steps are the same as in Specific Implementation Methods One to Nine.

[0039] The beneficial effects of the present invention are verified using the following embodiments:

[0040] Example 1: A multi-barrier coupling treatment process for organic complexed heavy metals in wastewater from battery cathode material production, specifically completed according to the following steps:

[0041] 1. Wastewater from the production of nickel-cobalt-manganese ternary precursors discharged by a battery company is fed into an equalization tank, and then the water volume and quality are homogenized. Then, the pH value of the wastewater is adjusted to 4.0 using sulfuric acid with a mass fraction of 20%, resulting in pH-adjusted wastewater.

[0042] In step one, the water quantity and quality are homogenized by a stirring device installed at the bottom of the regulating tank.

[0043] 2. The pH-adjusted wastewater is pumped into the oxidation reaction tank, and then 10% FeSO4·7H2O solution and 15% peracetic acid solution are added. The reaction is carried out under stirring for 60 minutes. The generated ·OH and organic free radicals synergistically break the metal-organic complex bond to obtain the effluent from the oxidation reaction tank.

[0044] The dosage of FeSO4·7H2O solution mentioned in step two is 0.2 g / L;

[0045] Fe added in step two 2+ The molar ratio with peracetic acid is 1:3;

[0046] 3. The effluent from the oxidation reaction tank enters the inclined tube sedimentation tank, and then a 30% NaOH solution is added to adjust the pH value of the wastewater to 10.2. Then, coagulant and coagulant aid are added in sequence to complete physical sedimentation. The generated sludge is sent to the sludge treatment system, and the supernatant enters the intermediate water tank.

[0047] The coagulant mentioned in step three is polyaluminum chloride;

[0048] The coagulant aid mentioned in step three is polyacrylamide;

[0049] The dosage of the coagulant mentioned in step three is 200 mg / L, and the dosage of the coagulant aid is 3 mg / L.

[0050] The hydraulic retention time of the inclined tube sedimentation tank mentioned in step three is 2 hours;

[0051] 4. Add dilute hydrochloric acid to the intermediate water tank and use 5% dilute hydrochloric acid to adjust the pH value of the wastewater back to 6.2, so as to obtain wastewater with a pH value of 6.0~6.5;

[0052] 5. The wastewater with a pH of 6.2 is pumped into the deep adsorption system and flows through the primary adsorption unit and the secondary adsorption unit in sequence to obtain the wastewater treated by the deep adsorption system.

[0053] The primary adsorption unit described in step five is filled with activated carbon to physically intercept suspended solids and quench residual oxidants, thus protecting the subsequent resin.

[0054] The secondary adsorption unit described in step five is filled with iminodiacetic acid-type chelating resin to capture residual trace metal ions.

[0055] The iminodiacetic acid type chelating resin is model D402 and was purchased from Jiangsu Suqing Water Treatment Engineering Group Co., Ltd.

[0056] The empty bed velocity of both the primary adsorption unit and the secondary adsorption unit mentioned in step five is 5 BV / h;

[0057] VI. Wastewater treated by the deep adsorption system meets the relevant industry emission standards or reuse standards, achieving compliant discharge or reuse in production processes.

[0058] In Step 1 of Example 1, the wastewater contained a total nickel concentration of 125.6 mg / L, a total cobalt concentration of 48.2 mg / L, a COD concentration of 850 mg / L, and a pH of 8.5. The wastewater also contained a large amount of EDTA complexing agent. After treatment using the multi-barrier coupling treatment process for organic complexed heavy metals in the wastewater from the production of battery cathode materials in Example 1, the final effluent had a total nickel concentration of less than 0.05 mg / L, a total cobalt concentration of less than 0.02 mg / L, and a COD concentration of less than 50 mg / L, which met the emission limits for heavy metals from newly established enterprises as specified in the "Emission Standard of Pollutants for Battery Industry" (GB 30484-2013), thus achieving compliant emissions.

Claims

1. A multi-barrier coupled treatment process for organic complexed heavy metals in battery cathode material production wastewater, characterized in that The process is specifically completed according to the following steps:

1. The wastewater generated from battery production or recycling is fed into an equalization tank, where the water quantity and quality are homogenized. The pH value of the wastewater is then adjusted to 3.0-4.5 to obtain pH-adjusted wastewater.

2. The pH-adjusted wastewater is pumped into the oxidation reaction tank, and FeSO4·7H2O solution and peracetic acid solution are added. The reaction is carried out under stirring conditions for a period of time. The generated ·OH and organic free radicals synergistically break the metal-organic complex bond to obtain the effluent from the oxidation reaction tank.

3. The effluent from the oxidation reaction tank enters the inclined tube sedimentation tank, and then NaOH solution is added to adjust the pH value of the wastewater to 10.0~10.

5. Then, coagulant and coagulant aid are added in sequence to complete physical sedimentation. The generated sludge is sent to the sludge treatment system, and the supernatant enters the intermediate water tank.

4. Add dilute hydrochloric acid to the intermediate water tank to adjust the pH value of the wastewater back to 6.0~6.5, thus obtaining wastewater with a pH value of 6.0~6.5; 5. The wastewater with a pH value of 6.0~6.5 is pumped into the deep adsorption system and flows through the primary adsorption unit and the secondary adsorption unit in sequence to obtain the wastewater treated by the deep adsorption system. VI. Wastewater treated by the deep adsorption system meets the relevant industry emission standards or reuse standards, achieving compliant discharge or reuse in production processes.

2. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from production of a battery cathode material according to claim 1, characterized in that In step one, the pH value of the wastewater is adjusted to 3.0-4.5 using sulfuric acid or hydrochloric acid with a mass fraction of 10%-30%. In step one, the water quantity and quality are homogenized by a stirring device or aeration device installed at the bottom of the regulating tank.

3. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from production of a battery cathode material according to claim 1, characterized in that The total nickel concentration in the wastewater mentioned in step one is 10 mg / L to 500 mg / L, the total cobalt concentration is 5 mg / L to 200 mg / L, and the COD concentration is 200 mg / L to 1500 mg / L.

4. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from production of a battery cathode material according to claim 1, characterized in that The reaction time in step two is 45 min to 90 min; the mass fraction of the peracetic acid solution in step two is 15% to 20%.

5. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from production of battery cathode materials according to claim 1, characterized in that The FeSO4·7H2O solution mentioned in step two has a mass fraction of 10%; the dosage of the FeSO4·7H2O solution mentioned in step two is 0.1 g / L to 5 g / L.

6. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from battery cathode material production according to claim 1, characterized in that Fe added in step two 2+ Molar ratio with peroxoacetic acid is 1: (1-5).

7. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from battery cathode material production according to claim 1, characterized in that The NaOH solution mentioned in step three has a mass fraction of 30%; the coagulant mentioned in step three is polyaluminum chloride; and the coagulant aid mentioned in step three is polyacrylamide.

8. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from battery cathode material production according to claim 1, characterized in that The dosage of coagulant in step three is 100 mg / L to 300 mg / L, and the dosage of coagulant aid is 2 mg / L to 5 mg / L; the hydraulic retention time of the inclined tube sedimentation tank in step three is 1.5 h to 2.5 h.

9. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from battery cathode material production according to claim 1, characterized in that The mass fraction of the dilute hydrochloric acid mentioned in step four is 5%; the primary adsorption unit mentioned in step five is filled with activated carbon; the secondary adsorption unit mentioned in step five is filled with iminodiacetic acid-type chelating resin.

10. The multi-barrier coupled treatment process for organic complexed heavy metals in wastewater from production of a battery cathode material according to claim 9, characterized in that The iminodiacetic acid type chelating resin is of type D402; the empty bed velocity of the primary adsorption unit and the secondary adsorption unit in step five is 2~10 BV / h.