Study On The Efficiency Of ClO₂-assisted Coagulation Enhanced Ultrafiltration Treatment Of Lithium Battery Production Wastewater

At present,traditional fossil energy resources are increasingly depleted.And the adjustment of energy structure has made the lithium battery industry develop rapidly.The mass production of lithiumion batteries,coupled with the industrial pollution caused by the dismantling and recycling of a large amount of waste water after reaching the service life,is also a serious threat to human settlements and water ecological security.Lithium battery production wastewater has high biological toxicity and contains a large number of organic pollutants that are difficult to biodegrade,so it is tough for traditional wastewater treatment processes to make it up to the standard.The ultrafiltration water treatment technology has the advantages of being clean,simple and efficient,but the membrane fouling problem caused by wastewater affects its promotion in water treatment applications.Coagulation technology is safe and economical,which is often used as a pretreatment method in the field of water treatment.In addition,pre-oxidation treatment technology can not only strengthen the coagulation effect,but also become an effective way to alleviate membrane fouling.Therefore,starting from the pre-oxidation-assisted coagulation coupled ultrafiltration process to strengthen the treatment of lithium battery production wastewater,this paper gradually explores the treatment efficiency of different process combinations on lithium battery production wastewater and the mitigation of membrane fouling,and analyzes the membrane fouling mechanism under different working conditions.In this topic,polyaluminum ferric sulfate（PAFS）and titanium tetrachloride（TiCl₄）were selected as two coagulants for pretreatment of lithium battery production wastewater before membrane pretreatment,and its effect on PES ultrafiltration membrane treatment was explored.The effect of wastewater efficiency was investigated through the specific flux curve and irreversible and reversible fouling resistance change graphs of ultrafiltration membranes under different experimental conditions.The experiment found that when the p H was 8,the two coagulants could adsorb some organic pollutants in the lithium battery production wastewater at the optimal dosage（0.5 mg/L）.Moreover,the filter cake layer formed by the floc particles on the surface of the PES ultrafiltration membrane increases the water passage,which significantly improves the specific flux level of the PES ultrafiltration membrane.It is converted into transitional substances and hydrophilic substances under the action of the ultrafiltration membrane,the polarity of the ultrafiltration membrane surface is enhanced,the hydrophilicity is strengthened,the adhesion between the pollutants and the PES membrane is weakened,and the reversible pollution of the membrane is alleviated.Among them,the effect of TiCl₄ coagulant is better than that of PAFS coagulant,the specific flux is increased by 20.83%and 14.58%,the total organic carbon（TOC）removal rate of wastewater is increased by 24%and 20%,and the lithium battery production wastewater Contaminants containing unsaturated bonds are removed.In order to further study the auxiliary effect of ClO₂ and UV/ClO₂ pre-oxidation on coagulation-ultrafiltration and the effect of membrane fouling mitigation,the ratio of the membranes of the two coagulants to the treatment of lithium battery production wastewater with different dosages of ClO₂ was investigated.The flux curve and the change of fouling resistance were compared and analyzed,and the fouling mechanism of PES ultrafiltration membrane under this working condition was explored.In addition,this topic explores the removal mechanism of ClO₂ pre-oxidation on the removal of organic matter in lithium battery production wastewater by detecting the water quality indicators of the treatment and analyzing the Fourier transform infrared spectroscopy,combined with the changes in the hydrophilic and hydrophobic classification of the effluent after the membrane.Characterization methods were used to investigate the distribution of pollutants on the surface of PES membranes under different treatment conditions.Finally,it is found that for PAFS coagulant,when the dosage of ClO₂ is 1mg/L,the improvement effect of PES membrane specific flux level（16.67%）and the mitigation effect of membrane fouling are the most significant,and it also shows a certain degree of reversible fouling.For TiCl₄ coagulant,ClO₂ pre-oxidation treatment can effectively alleviate the irreversible pollution caused by pure coagulation ultrafiltration process.The mitigation effect of pollution is the most significant.By comparison,it is found that after the pre-oxidation of ClO₂,the attractive force between the pollutants and the ultrafiltration membrane surface is converted into repulsion after PAFS coagulation,the interface is more stable,the pollutants are more difficult to deposit on the ultrafiltration membrane surface,and the TOC removal rate an increase of 27%.After UV activation,when the dosage of ClO₂ was 1 mg/L,the reversible pollution of the PES membrane after treatment with the two coagulants was reduced to a certain extent compared with the direct filtration,and the irreversible pollution increased.Under the same dosage,the removal efficiency of TOC decreased by 8%compared with that of ClO₂ alone pre-oxidation,and after PES membrane filtration,the deposition and aggregation of pollutant particles on the membrane surface was also more obvious than that of pure ClO₂ oxidation,especially.The distribution of interfacial energy on the surface of the PES ultrafiltration membrane was changed at high doses.For PAFS coagulants,contaminants in solution are more likely to deposit on the UF membrane surface.This paper proposes a combined process of UV/ClO₂,coagulation coupled with ultrafiltration water treatment to treat lithium battery production wastewater,and gradually explores the two coagulants for separate pretreatment,ClO₂ pre-oxidation coupled with two coagulants for pretreatment with UV/ClO₂ advanced pre-oxidation coupled with two coagulant pretreatments to investigate the pollution mitigation and water purification efficiency changes of the PES ultrafiltration membrane in the treatment of lithium battery production wastewater under different dosages of ClO₂.The membrane fouling mechanism under different experimental conditions was explored by means of Fourier transform infrared spectroscopy analysis,hydrophilic and hydrophobic grading changes and scanning electron microscopy characterization combined with mixed fouling model analysis,and finally some instructive conclusions were drawn.