Research On Removal Of Organic Pollutants From Water By Activating Persulfate With Catalysts Prepared From Spent Lithium Cobalt Oxide Batteries

In recent decades,lithium-ion batteries have been extensively utilized in mobile electronic devices,electric vehicles and grid energy storage devices for their long cycle life,high charge and discharge capacity,excellent thermal stability and high energy density,etc.A large number of spent lithium-ion batteries have also been gen erated.Heavy metals and toxic electrolytes in spent lithium-ion batteries can cause environ mental pollution;at the same time,the mineral resources necessary to produce lithium-ion batteries are dwindling,and there will be a shortage of raw materials.Therefore,a proper and efficient way to recycle spent lithium-ion batteries can not only reduce the pollution of the environment caused by toxic and harmful substances,but also promote sustainable development.The resource reuse of recycled materials from spent lithium-ion batteries is attracting increasing attention.The recovered materials could not only be used as feedstock for electrodes,but also as precursors to prepare multifunctional materials.Widening the utilization pathways of recovered materials,and the functional and high value utilization of them are also the focus of current research.This study aims to explore a new strategy for functionalized utilization of recovered waste lithium-ion battery materials.Using spent mobile phone lithium-ion batteries as the target of the study,the recovered cathode and anode materials were used as precursors for the preparation of catalysts used in sulfate radical advanced oxidation processes（SR-AOPs）.SR-AOPs are an emerging process for the treatment of persistent organic pollutants in water,which usually employs heterogeneous transition me tal-based materials and carbon-based materials as catalysts to activate persulfates to generate highly reactive oxygen radicals for the degradation of pollutants.However,the complex synthesis process and high preparation cost of heterogeneous catalysts have limited their application.Considering that the cathode active material of spent lithium-ion batteries contains abundant transition metal elements and the anode active material generally consists of graphite carbon,this study proposed to use the recovered materials for the preparation of SR-AOPs catalysts,which can not only reduce the environmental pollution problem caused by spent lithium-ion batteries,but also provide excellent perfor mance and low cost catalysts for SR-AOPs.Energy saving and emission reduction through“turning waste into treasure"is of practical significance for the early achieve ment of the goal of"carbon peaking and carbon neutrali ty”.The specific contents and main conclusions of this paper are summa rized as follows:（1）Using spent mobile phone lithium-ion batteries as raw material,the cathode material was recovered through a pretreatment process,and used as precursors to prepare a series of CM catalysts for SR-AOPs through a calcination process.The structure and physicochemical properties were characterized using a series of characterization techniques,which showed that the main component of the CM catalyst was LiCoO ₂,with small amounts of other substances such as Co ₃O₄.The catalytic degradation experiments showed that CM-850 has the best catalytic activity and could efficiently activate peroxy mo nosulfate（PMS）with a removal rate of over 94%for 10 mg/L levofloxacin hydroch loride（LFX）within 60 min.The CM-850/PMS system could operate effectively over a wide pH range（3-9）.Moreover,CM-850 has good reusability,and the removal rate of LFX was still up to 80% after four cycles of experiments.Co²⁺in CM-850 acted as the active site to activate the PMS,while the redox cycle between Co²⁺and Co³⁺accelerated the activation of PMS.During the reaction,SO₄^·-,HO·,¹O₂ and·O₂^-were generated,in which the free radical oxidation pathway dominated by SO₄^·-and the non-free radical pathway dominated by ¹O₂ played a major role in the degradation of LFX.In addition,the CM-850/PMS system showed good performance in the degradation of LFX in natural waters as well as other antibiotics.（2）Compared with cathode materials in spent lithium-ion batteries,there has been less research on the recycling of anode materials due to their relatively low added value and expensive and complicated purification steps.Therefore,a strategy for the recycling of anode materials was explored,whereby AM catalysts with abundant mesopores were successfully synthesized by a simple calcination process using copper foil and graphite carbon in the recovered spent anode electrodes as raw materials.The characterization results indicated that the AM catalyst was a CuO/C composite.Subsequently,the effectiveness of AM catalyst for the activation of PMS to degrade Rhoda mine B（RhB）was evaluated,and the effects of various reaction conditions on the degradation were investigated.In the AM/PMS system,the removal rate of RhB（20 mg/L）reached 100%within 13 min,and the catalyst exhibited good perfor mance in the removal of various dyes and antibiotic organic pollutants.The combination of metal oxide/carbon materials enables the AM catalyst to have good electrical conductivity,which could be used as electron transfer medium during the reaction to accelerate the electron transfer between PMS and RhB,thus facilitating the degradation of RhB.The redox cycle between Cu（II）and Cu（I）in the AM catalyst could effectively activate the PMS to produce reactive oxygen species,in which SO ₄^·-played a major role in the degradation of RhB,followed by ¹O₂ and·O₂^-.（3）The effect of preparation temperature on the catalytic perfor mance and mechanism of the catalysts derived from spent anode materials was investigated.Using recovered anode materials as raw materials,the catalysts were prepared at two different calcination temperatures,and ciprofloxacin（CIP）,a common antibiotic contaminant in water,was selected as the target contaminant.The performance of the two catalysts for activating PMS to degrade CIP was investigated,and the correlation between their compositions and catalytic activity and mechanism was focused on.The reactive oxygen species generated during the activation of PMS by the two catalysts and the activation mechanism were compared and analyzed based on free radical quenching experiment,electron para magnetic resonance spectroscopy,PMS decomposition and electrochemical test results.In the AM-850/PMS system,PMS broke down more quickly and was able to generate more free radicals,while CIP degradation relied mainly on the free radical pathway.In contrast,AM-450 has a higher graphite carbon content and prone to electron transfer,in the system the degradation of CIP mainly depended on the non-radical pathway of electron transfer.The CIP removal process followed the pseudo-first-order kinetic equation,with rate constants of 0.0514 min^-1 and 0.0315min^-1 in the AM-450/PMS and AM-850/PMS systems,respectively.Therefore,the surface electron transfer-do minated non-free radical pathway could degrade pollutants more rapidly than the free radical pathway.（4）The heterogeneous metal-based catalysts prepared fro m spent mobile phone lithium-ion batteries exhibited excellent catalytic activity,but the problem of metal ion leaching was still unavoidable.Therefore,a series of non-metallic carbon-based catalysts were prepared to activate PMS for the degradation of atrazine（ATZ）using anode graphite carbon recovered from spent mobile phone lithium-ion batteries as raw material,and the impact of catalysts and ATZ degradation products on the ecological environ ment was evaluated.TG-800 exhibited optimal catalytic perfor mance,achieving 99.2%degradation of ATZ within 6 min,which could be attributed to the abundant oxygen-containing functional groups（especially C=O and C-O）on the surface of TG-800.In the TG-800/PMS system,ATZ could be degraded by both free radical pathways(SO ₄^·-,HO·and·O₂^-)and non-radical pathways（¹O₂ and direct electron transfer）.The degradation of ATZ mainly involved the attack of reactive atoms with high Fukui indices in the ATZ molecule by the generated reactive species,triggering side chain dealkylation,dechlorination-hydroxylation,side chain alkyl oxidation,side chain olefination and dehydrogenation,and finally decomposition and mineralization to small molecule products.The results of the toxicity assessment de monstrated that ATZ molecule could be degraded to less toxic or even non-toxic intermediates in the TG-800/PMS system and that the TG-800 catalyst did not cause secondary contamination.The TG-800/PMS system also exhibited universal applicability for the degradation of antibiotic contaminants and was effective in degrading ATZ in real water samples,while demonstrating good reusability.In summary,the heterogeneous metal-based catalysts,metal-carbon composite catalysts and carbon-based catalysts prepared from lithium-ion batteries of waste mobile phones coupled with PMS advanced oxidation technology for the remediation of organic polluted wastewater such as antibiotics,dyes and pesticides are highly effective and have potential for practical application.This study laid a theoretical foundat ion for combining the field of waste lithium-ion battery recycling and refractory organic wastewater treatment.