【作者】 郭宇；

【导师】 陈标华； 于刚强； 胡雪生；

【作者基本信息】 北京工业大学 ， 环境工程（专业学位）， 2024， 硕士

【摘要】 电动汽车行业的飞速发展导致了锂离子电池（LIBs）需求量的不断增加,尽管电动汽车退役的锂离子电池可以在储能等行业中被重复使用,但它们终将不可避免地被丢弃。这些废锂离子电池中不仅含大量锂和钴等有价值的金属,而且其所含电解质的毒性极强,如果不对废锂离子电池加以回收利用,将导致资源的巨大浪费和严重的生态毒性,并对人类健康造成重大影响。湿法冶金作为我国应用最广泛的废锂离子电池的回收方法,具有高选择性和低能耗的特点,其策略是使用溶剂将正极材料中的金属元素转化为水溶液,最终从水溶液中进行目标产品分离和提纯。溶剂萃取法因操作简单、选择性高和适应性强等优点在金属分离中有着广泛的应用,然而传统有机萃取剂的萃取效率有限,加上其高挥发性和环境污染问题,从而在一定程度上限制了其潜力。离子液体（IL）和低共熔溶剂（DES）具有绿色、高效和结构可调节性等特点,可以作为传统有机萃取剂的良好替代品,广泛应用于化学分离领域。基于此,本研究提出利用IL和DES作为萃取剂替代传统有机溶剂进行废锂离子电池中有价金属的分离研究。提出了两种新型协同萃取系统（1-胺丙基-3-甲基咪唑双（三氟甲基）磺酰基）亚胺盐（[APMIM][Tf₂N]）协同三正辛基/己基氧化膦混合物（C923）萃取体系和疏水性DES（正癸酸:利多卡因=1:1）协同磷酸三丁酯（TBP）萃取体系)用于从废三元LIBs(Li Ni_0.5Mn_0.3Co_0.2O₂)的模拟盐酸浸出液中选择性萃取有价金属,本文研究内容如下:（i）分别以[APMIM][Tf₂N]/C923和疏水性DES/TBP为萃取剂,研究有价金属离子(Li⁺、Ni²⁺、Co²⁺和Mn²⁺)的选择性萃取性能（即萃取效率和选择性）,并进一步优化萃取条件。结果表明,在[APMIM][Tf₂N]/C923系统中,p H=4.0、m_IL=30wt%、A/O=1:4时,Ni²⁺、Co²⁺和Mn²⁺的萃取效率分别为97.74%、99.87%和99.98%。β_Li+/Ni2+、β_Li+/Co2+和β_Li+/Mn2+的分离选择性分别高达227.60、5129.97和46206.73;在疏水性DES/TBP系统中,氢键供体:氢键受体（HBD:HBA）=1:1、p H=3.0、V_DES=70%、A/O=1:3时,Ni²⁺、Co²⁺和Mn²⁺的萃取效率分别为99.83%、99.07%和95.94%。β_Li+/Ni2+、β_Li+/Co2+和β_Li+/Mn2+的分离选择性分别为3254.31、583.66和129.97。两种新型协同萃取系统萃取后的萃余液中均富集了高纯度Li⁺;（ii）从[APMIM][Tf₂N]/C923系统反萃有价金属,Ni²⁺、Co²⁺和Mn²⁺的反萃率分别为94.37%、95.61%和99.15%;从疏水性DES/TBP系统反萃有价金属,Ni²⁺、Co²⁺和Mn²⁺的反萃率分别为96.8%、98.8%和71.4%。Li⁺和Co²⁺分别以碳酸锂（92.3 wt.%）和草酸钴（94.9 wt.%）的形式被回收。再生[APMIM][Tf₂N]/C923和疏水性DES/TBP萃取系统即使在多次循环后也表现出良好的萃取性能;（iii）光谱学研究表明两种新型协同萃取系统均遵循所谓的“阳离子交换机制”,P=O官能团在萃取过程中发挥着重要作用。[APMIM][Tf₂N]和C923间存在协同萃取效应,相似地,疏水性DES与TBP之间也存在类似作用。萃合比实验表明,[APMIM][Tf₂N]/C923系统中Ni²⁺、Co²⁺和Mn²⁺可以分别与3、1和1分子C923形成络合物;疏水性DES/TBP系统中Ni²⁺、Co²⁺和Mn²⁺可以分别与5个、4个和6个TBP分子形成络合物。热力学参数表明萃取过程是一个自发有序的放热过程（即ΔH<0、ΔG<0和ΔS<0）。（iv）通过量子化学计算（QC）从分子水平揭示萃取机制和分子间相互作用。金属离子可以在水溶液中形成水合离子,有机萃取剂在破坏水合相互作用中发挥作用,这可以通过金属离子-H₂O和金属离子萃取剂结合能的差异来表现。[APMIM][Tf₂N]系统中,结合能分析表明,Co²⁺、Ni²⁺和Mn²⁺倾向于与萃取剂结合,而不是与水分子结合。另一方面,当Li⁺与过渡金属竞争萃取剂分子时,Li⁺处于劣势,这导致过渡金属和Li⁺之间的高选择性。独立梯度模型（IGMH）和静电势（ESP）的分析也证实了选择性萃取的机制,其中静电相互作用和配位作用在形成M-[Tf₂N]^--C923（M代表Co、Ni、Mn）的络合物中起主导作用;在疏水性DES/TBP系统中,过渡金属离子与DES/TBP之间的M²⁺-Dec A^-静电作用和P=O→M配位相互作用共同主导了金属离子的萃取,Ni²⁺/Co²⁺/Mn²⁺与DES/TBP之间的相互作用强度强于Li⁺与DES/TBP之间的相互作用,导致过渡金属离子的水合络合物比Li⁺的水合络合物更容易断裂。因此,更多的Ni²⁺/Co²⁺/Mn²⁺从水相提取到有机相中,并且Li⁺保留在水相中,这导致高分离选择性。更多还原

【Abstract】 The rapid development of the electric vehicle industry has led to an increasing demand for lithium-ion batteries（LIBs）.Although retired LIBs from electric vehicles can be reused in industries such as energy storage,they will inevitably be discarded.These waste LIBs not only contain a large number of valuable metals such as lithium and cobalt,but also contain highly toxic electrolytes.If waste LIBs are not recycled,it will lead to huge waste of resources and serious ecological toxicity,and have a significant impact on human health.Hydrometallurgy,as the most widely used method for recycling waste LIBs in China,has the characteristics of high selectivity and low energy consumption.Its strategy is to use solvents to convert metal elements in cathode materials into aqueous solutions,and ultimately separate and purify the target product from the aqueous solution.The solvent extraction method has been widely used in metal separation due to its advantages of simple operation,high selectivity,and strong adaptability.However,the extraction efficiency of traditional organic extractants is limited,coupled with their high volatility and environmental pollution issues,which to some extent limit their potential.Ionic liquids（IL）and deep eutectic solvents（DES）have the characteristics of being green,efficient,and structurally adjustable,and can be widely used as good alternatives to traditional organic extractants in the field of chemical separation.Based on this,this study proposes to use IL and DES as extractants to replace traditional organic solvents for the separation of valuable metals in waste LIBs.Two novel synergistic extraction systems（1-aminopropyl-3-methylimidazolium bis（trifluoromethyl）sulfonyl）imide（[APMIM][Tf₂N]）synergistic tri-n-octyl/hexyl phosphine oxide mixture（C923）extraction system and hydrophobic DES（decanoic acid:lidocaine=1:1）synergistic tributyl phosphate（TBP）extraction system)were proposed for selective extraction of valuable metals from simulated hydrochloric acid leaching solution of waste ternary LIBs(Li Ni_0.5Mn_0.3Co_0.2O₂).The research content of this studies are as follows:（i）Using[APMIM][Tf₂N]/C923 and hydrophobic DES/TBP as extractants,the selective extraction performance（i.e.extraction efficiency and selectivity）of valuable metal ions(Li⁺,Ni²⁺,Co²⁺,and Mn²⁺)was studied,and the extraction conditions were further optimized.The results showed that in the[APMIM][Tf₂N]/C923 system,the extraction efficiencies of Ni²⁺,Co²⁺,and Mn²⁺were 97.74%,99.87%,and 99.98%,respectively,at p H=4.0,m _IL=30wt%,and A/O=1:4.The separation selectivity ofβ_Li+/Ni2+,β_Li+/Co2+andβ_Li+/Mn2+is as high as 227.60,5129.97,and 46206.73,respectively;In a hydrophobic DES/TBP system,when hydrogen bond donor:hydrogen bond acceptor（HBD:HBA）=1:1,p H=3.0,V_DES=70%,and A/O=1:3,the extraction efficiency of Ni²⁺,Co²⁺,and Mn²⁺is 99.83%,99.07%,and 95.94%,respectively.The separation selectivity ofβ_Li+/Ni2+,β_Li+/Co2+andβ_Li+/Mn2+is 3254.31,583.66,and 129.97,respectively.High purity Li⁺was enriched in the residual solution of two new collaborative extraction systems;（ii）Valuable metals were stripped from the[APMIM][Tf₂N]/C923 system,and the stripping efficiency of Ni²⁺,Co²⁺,and Mn²⁺were 94.37%,95.61%,and 99.15%,respectively;The stripping efficiency of Ni²⁺,Co²⁺,and Mn²⁺in hydrophobic DES/TBP system were 96.8%,98.8%,and 71.4%,respectively.Li⁺and Co²⁺were recovered in the form of lithium carbonate（92.3 wt.%）and cobalt oxalate（94.9 wt.%）,respectively.The regenerated[APMIM][Tf₂N]/C923 and hydrophobic DES/TBP extraction system exhibit good extraction performance even after multiple cycles;（iii）Spectroscopic studies have shown that both novel synergistic extraction systems follow the so-called"cation exchange mechanism",where the P=O functional group plays an important role in the extraction process.There is a synergistic extraction effect between[APMIM][Tf₂N]/C923,and similarly,there is a similar effect between hydrophobic DES/TBP.The slope experiment showed that Ni²⁺,Co²⁺,and Mn²⁺in the[APMIM][Tf₂N]/C923 system can form complexes with 1,3,and 1molecule C923,respectively;In hydrophobic DES/TBP systems,Ni²⁺,Co²⁺,and Mn²⁺can form complexes with 5,4,and 6 TBP molecules,respectively.The thermodynamic parameters indicate that the extraction process is a spontaneously ordered exothermic process（i.eΔH<0ΔG<0 andΔS<0）.（iv）Revealing extraction mechanisms and intermolecular interactions at the molecular level through quantum chemical calculations（QC）.Metal ions can form hydrated ions in aqueous solutions,and organic extractants play a role in disrupting hydration interactions,which can be demonstrated by the difference in binding energy between metal ion H₂O and metal ion extractants.In the[APMIM][Tf₂N]/C923system,binding energy analysis indicates that Ni²⁺,Co²⁺,and Mn²⁺tend to bind with the extractant rather than with water molecules.On the other hand,when Li⁺competes with transition metals for extractant molecules,Li⁺is at a disadvantage,resulting in high selectivity between transition metals and Li⁺.The analysis of independent gradient model based on Hirshfeld partition（IGMH）and electrostatic potential（ESP）also confirmed the mechanism of selective extraction,where electrostatic interactions and coordination play a dominant role in the formation of M-[Tf₂N]^--C923 complexes;In hydrophobic DES/TBP systems,the M²⁺-Dec A electrostatic interaction and P=O→M coordination interaction between transition metal ions and DES/TBP jointly dominate the extraction of metal ions.The interaction strength between Ni²⁺/Co²⁺/Mn²⁺and DES/TBP is stronger than that between Li⁺and DES/TBP,resulting in the hydrated complexes of transition metal ions being more prone to breakage than those of Li⁺.Therefore,more Ni²⁺/Co²⁺/Mn²⁺is extracted from the aqueous phase into the organic phase,and Li⁺is retained in the aqueous phase,resulting in high separation selectivity.更多还原