Method for treating battery recovery wastewater by irradiation

Abstract

The invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for treating battery recovery wastewater by irradiation, which comprises the following steps: (1) adjusting the pH value of lithium battery recovery wastewater to 2.5-4.0, adding a catalyst containing soluble ferrite, and mixing; (2) carrying out electron beam irradiation on the lithium battery recovery wastewater added with the catalyst; and (3) adjusting the pH value of the irradiated lithium battery recovery wastewater to 7.5-9.5, standing and precipitating, and taking the supernatant to obtain the treated wastewater.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, and specifically relates to a method for treating battery recycling wastewater by irradiation. Background Technology

[0002] With the explosive growth of the new energy vehicle industry, the recycling of spent lithium-ion batteries has become an inevitable trend. The hydrometallurgical process of battery recycling generates a large amount of complex wastewater. This wastewater not only contains high concentrations of heavy metals such as nickel, cobalt, manganese, and lithium, but also high concentrations of recalcitrant organic matter and fluorides. These organic compounds mainly originate from battery electrolyte solvents (such as carbonates) and their decomposition products, binder solvents (NMP), etc., resulting in extremely high chemical oxygen demand (BOD) and poor biodegradability (BOD / COD < 0.3). Direct discharge would cause serious environmental pollution, and traditional biological treatment methods are extremely ineffective. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention proposes a method for irradiating battery recycling wastewater. This method can rapidly degrade and mineralize organic matter in battery recycling wastewater, effectively improve the biodegradability of the wastewater, and achieve efficient wastewater purification.

[0004] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for irradiating wastewater from battery recycling includes the following steps: (1) After adjusting the pH of the lithium battery recycling wastewater to 2.5-4.0, add a catalyst containing soluble ferrous salt and mix. (2) Electron beam irradiation of lithium battery recycling wastewater containing catalyst; (3) Adjust the pH of the irradiated lithium battery recycling wastewater to 7.5-9.5, let it stand to settle, and then take the supernatant to obtain the treated wastewater.

[0005] In one embodiment, in step (1), the catalyst is a mixture of soluble ferrous salt and soluble copper salt.

[0006] In one embodiment, Fe in the catalyst 2+ With Cu 2+ The molar ratio is (10-30):1.

[0007] In one embodiment, the soluble ferrous salt is at least one of ferrous sulfate and ferrous chloride.

[0008] In one embodiment, the soluble copper salt is at least one of copper sulfate and copper chloride.

[0009] In one embodiment, in step (1), the amount of catalyst added is based on Fe 2+ The concentration is calculated to be 100-500 mg / L.

[0010] In one embodiment, in step (1), if the fluoride concentration in the lithium battery recycling wastewater is >200mg / L, calcium chloride is added first and then filtered to pretreat the lithium battery recycling wastewater so that the fluoride concentration in it is reduced to ≤200mg / L.

[0011] In one embodiment, in step (1), the lithium battery recycling wastewater is derived from the raffinate, mother liquor, dismantling and washing wastewater or cathode material preparation wastewater of the hydrometallurgical process, with a chemical oxygen demand concentration of 500-20000 mg / L and a fluoride concentration of 10-500 mg / L.

[0012] In one embodiment, in step (2), lithium battery recycling wastewater is irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 10-30 mm.

[0013] In one embodiment, the flow rate of the lithium battery recycling wastewater is 0.5-5 m / s.

[0014] In one embodiment, in step (2), the energy of the electron beam irradiation is 3-6 MeV, the electron beam current is 2-5 mA, and the electron beam dose in the irradiated area is 50-200 kGy.

[0015] In one embodiment, in step (2), oxygen-containing gas is introduced into the lithium battery recycling wastewater while the wastewater is being irradiated with an electron beam.

[0016] In one embodiment, the oxygen-containing gas is air, oxygen, or ozone.

[0017] In one embodiment, the aeration rate of oxygen-containing gas introduced into each liter of wastewater is 1-5 L / min.

[0018] In one embodiment, when the COD concentration in the initial lithium battery recycling wastewater is ≤5000mg / L, the aeration rate of oxygen-containing gas introduced into each liter of wastewater is 1-2L / min; when the COD concentration in the initial lithium battery recycling wastewater is >5000mg / L, the aeration rate of oxygen-containing gas introduced into each liter of wastewater is 3-5L / min.

[0019] In one embodiment, the oxygen-containing gas is introduced via bottom micropore aeration, with the bubble diameter controlled between 10-100 μm.

[0020] In one embodiment, in step (3), the precipitation time is 30-60 min.

[0021] In one embodiment, the wastewater obtained after treatment in step (3) is fed into a biochemical treatment unit for further treatment.

[0022] In one embodiment, the biochemical treatment unit is an aerated biofilter or a membrane bioreactor.

[0023] The beneficial effects of this invention are: (1) In the method for treating battery recycling wastewater of the present invention, after adjusting the wastewater to a specific pH, a catalyst containing soluble ferrous salt is added, followed by electron beam irradiation. After electron beam irradiation, a large amount of ·OH (hydroxyl radicals) is generated in the wastewater. - (Hydrated electrons), H2O2, and H·, among which ·OH is an extremely strong oxidant that can non-selectively decompose most organic matter in wastewater. Under specific pH conditions, H2O2 generated by electron beam irradiation reacts with Fe²⁺. + This constitutes a highly efficient Fenton-like reaction, and the reaction equation is: Fe 2+ +H₂O₂→Fe 3+ + OH+OH - This significantly increases the yield of ·OH, thereby greatly improving the decomposition rate of organic matter in wastewater. Simultaneously, the eaq generated by electron beam irradiation... - It has extremely strong reducing properties and can rapidly reduce the Fe produced by Fenton-like reactions. 3+ Reduced to Fe 2+ (eaq) - +Fe 3+ →Fe 2+ This breaks the traditional Fenton regeneration (Fe) 3+ +H₂O₂→Fe 2+ +·OOH+H + Fe 2+ The slow rate bottleneck is overcome by using electron beam irradiation in conjunction with a Fenton-like reaction to achieve a synergistic effect, thus solving the problems of H2O2 supply efficiency and Fe in the traditional Fenton reaction. 3+ / Fe 2+ This addresses the two core challenges of cycle rate and significantly amplifies the energy utilization efficiency of the electron beam, efficiently converting primary active materials (such as H2O2) generated by the electron beam into more and more effective substances. The presence of OH allows the entire chain reaction to proceed at an extremely high speed, significantly increasing the yield and utilization rate of ·OH. It effectively degrades recalcitrant organic compounds such as carbonates and NMP, achieving a COD removal rate of over 78% in battery recycling wastewater.

[0024] (2) In the method for treating battery recycling wastewater of the present invention, the catalyst is preferably a mixture of soluble ferrous salt and soluble copper salt in a specific ratio. After the soluble ferrous salt and soluble copper salt dissolve in the lithium battery recycling wastewater, Fe is formed. 2+-Cu 2+ Bimetallic catalytic system, combined with electron beam irradiation, Cu 2+ It can also undergo a Fenton-like reaction: Cu 2+ +H₂O₂→Cu + +HO2·+H + Cu + +H₂O₂→Cu 2+ + OH+OH This accelerates the generation rate and utilization of ·OH, increasing the ·OH yield by 40%-60% compared to single ferrous salt catalysis. It can rapidly degrade recalcitrant organic matter (such as phosphate esters and amide extractants) and heavy metal complexes (cobalt, nickel, and lithium complexes) in wastewater, solving the problem of incomplete degradation by single catalysis. Furthermore, Cu… + It can promote Fe 3+ Rapid reduction to Fe 2+ (Cu) + +Fe 3+ →Cu 2+ +Fe 2+ ), to avoid Fe 3+ Accumulation leads to catalyst deactivation, prolonging the stable action time of the catalytic system and ensuring uniform catalytic effect during irradiation. Subsequently, when the pH is adjusted to 7.5-9.5, Cu... 2+ It will form Cu(OH)2 precipitate, which can synergistically adsorb residual heavy metal ions in wastewater and form a complex precipitation system with Fe(OH)3, further reducing the heavy metal content in the treated wastewater.

[0025] (3) In the method for treating battery recycling wastewater of the present invention, oxygen-containing gas can be introduced simultaneously with electron beam irradiation, which can capture the eaq generated by the electron beam. - It reacts with H· to generate superoxide radicals (·O2). - ) and its protonated form (·HO2), which further react to generate H2O2. The in-situ generated H2O2 can immediately participate in subsequent Fenton-like reactions, thereby generating more ·OH, thus enabling the energy of the electron beam to be used more fully for pollutant degradation.

[0026] (4) The method of treating battery recycling wastewater of the present invention further ensures the removal rate of organic matter in battery recycling wastewater by irradiating the lithium battery recycling wastewater in a thin layer of a specific thickness through the irradiation window of the electron beam irradiation reactor and optimizing the key parameters of electron beam irradiation energy and ventilation rate.

[0027] (5) The method of treating battery recycling wastewater of the present invention is environmentally friendly, does not require the addition of external H2O2, and does not introduce harmful chemicals in the treatment process, which meets the requirements of green environmental protection. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] Example 1: The battery recycling wastewater is the raffinate from the hydrometallurgical process of a lithium battery recycling plant. The wastewater has a COD of 6592 mg / L, pH of 1.8, BOD / COD ratio of 0.25, and fluoride concentration of 119 mg / L.

[0030] A method for irradiating wastewater from battery recycling includes the following steps: (1) Take 1L of wastewater, add NaOH solution to adjust the pH to 2.5, then add ferrous chloride as a catalyst and mix, so that the Fe in the wastewater... 2+ The concentration is 100 mg / L; (2) The wastewater with added catalyst was irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 10 mm. The flow rate was 5 m / s. At the same time, oxygen was introduced into the wastewater through the bottom micropores. The bubble diameter was controlled at 10-100 μm. The aeration rate of oxygen-containing gas per liter of wastewater was 3.5 L / min. The energy of electron beam irradiation was 3 MeV, the electron beam current was 2 mA, and the electron beam dose in the irradiation area was 50 kGy. (3) The pH of the irradiated water was adjusted to 7.5 with NaOH solution and allowed to stand for 30 min to settle. The supernatant was the wastewater obtained after treatment. The supernatant was tested and found to have COD=2110mg / L, organic matter removal rate reached 68.0%, BOD / COD=0.43. (4) The supernatant is introduced into the aerated biological filter for treatment until it meets the “GB 30484-2013 Battery Industry Pollutant Emission Standard” before being discharged.

[0031] Example 2: The battery recycling wastewater is the raffinate from the hydrometallurgical process of a lithium battery recycling plant. The wastewater has a COD of 7361 mg / L, pH of 1.7, BOD / COD ratio of 0.24, and fluoride concentration of 326 mg / L.

[0032] A method for irradiating wastewater from battery recycling includes the following steps: (1) Take 1L of wastewater, first add calcium chloride to make the Ca²⁺ in the wastewater equal to the total Ca²⁺. + When the concentration reached 450 mg / L, the reaction was stirred for 50 min, and the calcium fluoride precipitate was removed by filtration. At this point, the fluoride concentration dropped to 82 mg / L. (2) Add NaOH solution to the wastewater to adjust the pH to 4.0, then add ferrous sulfate as a catalyst and mix to make the Fe in the wastewater...2+ The concentration was 500 mg / L; (3) The wastewater containing the catalyst was irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 30 mm. The flow rate was 0.5 m / s. At the same time, oxygen was introduced into the wastewater through the bottom micropores. The bubble diameter was controlled at 10-100 μm. The aeration rate of oxygen-containing gas per liter of wastewater was 3.5 L / min. The energy of the electron beam irradiation was 6 MeV, the electron beam current was 5 mA, and the electron beam dose in the irradiation area was 200 kGy. (4) The pH of the irradiated water was adjusted to 9.5 with NaOH solution and allowed to stand for 60 min to settle. The supernatant was the wastewater obtained after treatment. The supernatant was tested and found to have COD=2069mg / L, organic matter removal rate reached 71.9%, and BOD / COD=0.45. (5) The supernatant is introduced into the aerated biological filter for treatment until it meets the “GB 30484-2013 Battery Industry Pollutant Emission Standard” before being discharged.

[0033] Example 3: The battery recycling wastewater is the raffinate from the hydrometallurgical process of a lithium battery recycling plant. The wastewater has a COD of 8523 mg / L, pH of 1.5, BOD / COD ratio of 0.21, and fluoride concentration of 280 mg / L.

[0034] A method for irradiating wastewater from battery recycling includes the following steps: (1) Take 1L of wastewater, first add calcium chloride to make the Ca²⁺ in the wastewater equal to the total Ca²⁺. + When the concentration reaches 500 mg / L, stir the reaction for 30 min, filter to remove calcium fluoride precipitate, and at this time the fluoride concentration drops to 95 mg / L; (2) Add NaOH solution to the wastewater to adjust the pH to 3.0, then add ferrous sulfate as a catalyst and mix to make the Fe in the wastewater... 2+ The concentration was 150 mg / L; (3) The wastewater with added catalyst was irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 20 mm. The flow rate was 1 m / s. At the same time, oxygen was introduced into the wastewater through the bottom micropores. The bubble diameter was controlled at 10-100 μm. The aeration rate of oxygen-containing gas per liter of wastewater was 4 L / min. The energy of electron beam irradiation was 5 MeV, the electron beam current was 3 mA, and the electron beam dose in the irradiation area was 180 kGy. (4) The pH of the irradiated water was adjusted to 9.0 with NaOH solution and allowed to stand for 40 min to settle. The supernatant was the wastewater obtained after treatment. The supernatant was tested and found to have COD=1816mg / L, organic matter removal rate reached 78.7%, BOD / COD=0.52. (5) The supernatant is introduced into the aerated biological filter for treatment until it meets the “GB 30484-2013 Battery Industry Pollutant Emission Standard” before being discharged.

[0035] Example 4: (The difference from Example 3 is the addition of ferrous sulfate and copper sulfate as catalysts) The battery recycling wastewater is the raffinate from the hydrometallurgical process of a lithium battery recycling plant. The wastewater has a COD of 8523 mg / L, pH of 1.5, BOD / COD ratio of 0.21, and fluoride concentration of 280 mg / L.

[0036] A method for irradiating wastewater from battery recycling includes the following steps: (1) Take 1L of wastewater, first add calcium chloride to make the Ca²⁺ in the wastewater equal to the total Ca²⁺. + When the concentration reaches 500 mg / L, stir the reaction for 30 min, filter to remove calcium fluoride precipitate, and at this time the fluoride concentration drops to 95 mg / L; (2) Add NaOH solution to the wastewater to adjust the pH to 3.0, then add ferrous sulfate and copper sulfate as catalysts and mix. The catalyst contains Fe 2+ With Cu 2+ The molar ratio is 20:1, and the Fe in the wastewater 2+ The concentration was 150 mg / L; (3) The wastewater with added catalyst was irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 20 mm. The flow rate was 1 m / s. At the same time, oxygen was introduced into the wastewater through the bottom micropores. The bubble diameter was controlled at 10-100 μm. The aeration rate of oxygen-containing gas per liter of wastewater was 4 L / min. The energy of electron beam irradiation was 5 MeV, the electron beam current was 3 mA, and the electron beam dose in the irradiation area was 180 kGy. (4) The pH of the irradiated water was adjusted to 9.0 with NaOH solution and allowed to stand for 40 min to settle. The supernatant was the wastewater obtained after treatment. The supernatant was tested and found to have a COD of 1065 mg / L, an organic matter removal rate of 87.5%, and a BOD / COD ratio of 0.61. (5) The supernatant is introduced into the aerated biological filter for treatment until it meets the “GB 30484-2013 Battery Industry Pollutant Emission Standard” before being discharged.

[0037] Comparative Example 1: (The difference from Example 3 is that no catalyst was added) The battery recycling wastewater is the raffinate from the hydrometallurgical process of a lithium battery recycling plant. The wastewater has a COD of 8523 mg / L, pH of 1.5, BOD / COD ratio of 0.21, and fluoride concentration of 280 mg / L.

[0038] A method for irradiating wastewater from battery recycling includes the following steps: (1) Take 1L of wastewater, first add calcium chloride to make the Ca²⁺ in the wastewater equal to the total Ca²⁺. + When the concentration reaches 500 mg / L, stir the reaction for 30 min, filter to remove calcium fluoride precipitate, and at this time the fluoride concentration drops to 95 mg / L; (2) Add NaOH solution to the wastewater to adjust the pH to 3.0; (3) The wastewater was irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 20 mm. The flow rate was 1 m / s. At the same time, oxygen was introduced into the wastewater through the bottom micropores. The bubble diameter was controlled at 10-100 μm. The aeration rate of oxygen-containing gas per liter of wastewater was 4 L / min. The energy of electron beam irradiation was 5 MeV, the electron beam current was 3 mA, and the electron beam dose in the irradiation area was 180 kGy. (4) The pH of the irradiated water was adjusted to 9.0 with NaOH solution and allowed to stand for 40 min to settle. The supernatant was the wastewater obtained after treatment. The supernatant was tested and found to have COD=4080mg / L, organic matter removal rate reached 52.1%, and BOD / COD=0.41.

[0039] (5) The supernatant is introduced into the aerated biological filter for treatment until it meets the “GB 30484-2013 Battery Industry Pollutant Emission Standard” before being discharged.

[0040] As can be seen from Examples 1 to 4, the method for treating battery recycling wastewater by irradiation of the present invention can achieve an organic matter removal rate of 68.0% or more in lithium battery recycling wastewater, increase the BOD / COD ratio to 0.43 or more, effectively improve the biodegradability of wastewater, and achieve efficient purification of wastewater.

[0041] Comparing Examples 3 and 4, it can be seen that when other conditions remain unchanged, adding both ferrous sulfate and copper sulfate as catalysts can further improve the removal rate of organic matter in wastewater and further enhance the purification effect of wastewater compared to using ferrous sulfate alone as a catalyst.

[0042] Comparing Example 3 and Comparative Example 1, it can be seen that when other conditions remain unchanged, using only electron beam irradiation without adding a catalyst will significantly reduce the removal efficiency of organic matter in wastewater.

Claims

1. A method for irradiating wastewater from battery recycling, characterized in that: Includes the following steps: (1) After adjusting the pH of the lithium battery recycling wastewater to 2.5-4.0, add a catalyst containing soluble ferrous salt and mix. (2) Electron beam irradiation of lithium battery recycling wastewater containing catalyst; (3) Adjust the pH of the irradiated lithium battery recycling wastewater to 7.5-9.5, let it stand to settle, and then take the supernatant to obtain the treated wastewater.

2. The method for recovering wastewater from irradiated batteries according to claim 1, characterized in that: In step (1), the catalyst is a mixture of soluble ferrous salt and soluble copper salt.

3. The method for irradiating and recovering wastewater from batteries according to claim 1, characterized in that: In step (1), the amount of catalyst added is based on Fe 2+ The concentration is calculated to be 100-500 mg / L.

4. The method for recovering wastewater from irradiated batteries according to claim 1, characterized in that: In step (1), the lithium battery recycling wastewater comes from the raffinate, mother liquor, dismantling and washing wastewater or cathode material preparation wastewater of the hydrometallurgical process, with a chemical oxygen demand concentration of 500-20000 mg / L and a fluoride concentration of 10-500 mg / L.

5. The method for recovering wastewater from irradiated batteries according to claim 1, characterized in that: In step (2), lithium battery recycling wastewater is irradiated with electron beam through the irradiation window of the electron beam irradiation reactor in a thin layer with a thickness of 10-30 mm.

6. The method for recovering wastewater from irradiated batteries according to claim 1, characterized in that: In step (2), the energy of the electron beam irradiation is 3-6 MeV, the electron beam current is 2-5 mA, and the electron beam dose in the irradiated area is 50-200 kGy.

7. The method for recovering wastewater from irradiated batteries according to claim 1, characterized in that: In step (2), oxygen-containing gas is introduced into the lithium battery recycling wastewater while the wastewater is being irradiated with an electron beam.

8. The method for irradiating and recovering wastewater from batteries according to claim 7, characterized in that: The aeration rate of oxygen-containing gas introduced into each liter of wastewater is 1-5 L / min.

9. The method for irradiating and treating battery wastewater according to claim 1, characterized in that: The ventilation method for introducing oxygen-containing gas is bottom micropore aeration, with the bubble diameter controlled at 10-100μm.

10. The method for irradiating and treating battery wastewater according to claim 1, characterized in that: In step (3), the precipitation time is 30-60 min.