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题名: 电子废弃物中稀贵金属的超临界流体回收方法与机理研究
作者: 刘康
学位类别: 博士
答辩日期: 2016-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 张付申
关键词: 含钯电子废料,废旧锂电池,稀贵金属,超临界水氧化机制,超临界二氧化碳萃取机理 ; Palladium-containing electronic waste, Spent lithium batteries, Rare precious metals, Supercritical water oxidation mechanism, Supercritical carbon dioxide extraction mechanism
其他题名: Recovery of Rare and Precious Metals from E-waste by Supercritical Fluids and Mechanisms Clarification
学位专业: 环境工程
中文摘要:       稀贵金属是电子废弃物资源化的主要经济驱动力之一。传统的稀贵金属回收技术(火法冶金、湿法冶金和生物冶金)存在易产生有毒有害烟气,步骤繁琐、有机试剂毒性大,菌种难培养、回收周期长的缺点。本研究以典型电子废弃物(废弃线路板,废弃陶瓷电容器和废旧锂电池)中的稀贵金属钯(Pd)和锂(Li)为主要研究对象,采用环境友好型的超临界流体技术实现了电子废弃物中稀贵金属Pd和Li的资源化,阐明了稀贵金属在不同超临界流体中的溶解和浸出机理,构建了超临界流体技术回收稀贵金属的绿色体系,为电子废弃物中稀贵金属的回收提供了快捷、高效和环保的新途径。本研究主要结论如下:
      (1) 研究了超临界水氧化法(SCWO)深度富集废弃线路板中Pd(0)的方法,阐明了溴化环氧树脂降解和Pd(0)的富集机理。研究发现NaOH/H2O2修饰后的SCWO系统可将溴化环氧树脂彻底降解为长链烃类 (CnH2n+2),CO2,H2O和NaBr。反应过程中,H2O2产生的HO•和HO2•引发了中间产物苯酚的氧化开环降解,提高了主要金属Cu的氧化程度,增强了Pd(0)的富集效率。NaOH通过亲核取代反应和消去反应提高了溴化环氧树脂在SCWO系统中的脱溴效率,并促进了主要元素Cu,Al和Ca向水合物或化合物的转变,同时引发的水汽置换反应和碱硅反应均不同程度地提高了NaOH/H2O2修饰的SCWO系统对Pd(0)的富集效率。
      (2) 研究了超临界二氧化碳 (SC-CO2)络合萃取废弃陶瓷电容器中Pd(II)的方法,阐明了Pd(II)在SC-CO2中与不同类型络合剂(Cyanex272、LIX84I和Cyanex302)的配位机理。研究发现废弃电容器中的Pd(0)可采用酸浸出-萃取剂络合的方法萃取。机理研究显示含中心S原子的萃取剂Cyanex302对Pd(II)的萃取效率大大优于中心原子为O的萃取剂Cyanex272和中心原子为N的萃取剂LIX84I。分子杂化轨道理论表明Pd(II)可以与Cyanex302的中心S原子形成π*键,这极大增强了所形成的中性络合物Pd(II)-Cyanex302在SC-CO2中的溶解度和稳定性。
       (3) 开发了SC-CO2直接萃取废弃线路板中Pd(0)的工艺。研究发现含钯富集体中的Pd(0)先被KI-I2组合利用氧化络合反应转化为碘络阴离子[PdI3]ˉ,随后[PdI3]ˉ与共溶剂丙酮通过电荷吸引力形成可溶于SC-CO2的含钯中性络合物 [(CH3COCH3)nH][PdI3]。该工艺无需利用酸造液将Pd(0) 转化为Pd(II),一步即可完成Pd(0)的萃取回收。相比传统贵金属回收工艺,利用SC-CO2作为溶剂回收废弃线路板中的Pd(0),具有回收步骤简洁、环境负荷小和不产生有机废液的优势。
       (4) 开发了亚/超临界水共处理废旧锂电池和废弃聚氯乙烯的工艺。利用废弃聚氯乙烯在亚/超临界水中脱氯产生的盐酸作为酸源,同步将锂电池正极材料锂钴酸中的金属锂和钴进行浸出。XRD、SEM-EDS和GC-MS表征表明废弃聚氯乙烯中的有机氯经过亚/超临界水共处理成功转化为金属锂和钴的无机氯配体,整个水热共处理过程无含氯有机物产生。该工艺可为废旧锂电池和废弃聚氯乙烯的无害化处理与资源化提供新的技术手段和回收方法。
英文摘要:        Rare and precious metals are one of the main economic driving force of e-waste recycling. Traditional e-waste recycling technologies (pyrometallurgy, hydrometallurgy and biometallurgy) of rare and precious metals have shortcomings such as the generation of poisonous and harmful gas, cumbersome recycling steps, toxicity of organic agents and long recovery periods. This work took the rare and precious metals palladium (Pd) and lithium (Li) in typical e-waste (Waste printed circuit boards: waste PCBs; Waste multilayer ceramic capacitor: W-MLCC; Spent lithium batteries: spent LIBs) as the main subjects. Environmentally friendly supercritical fluid technologies are employed to achieve the resourcfulization of rare and precious metals from electronic waste. The work constructed green recycling system of rare and precious metals in electronic waste based on supercritical fluid technology and clarified the dissolution and leaching mechanism of rare and precious metals in various supercritical fluids. It provides a fast, efficient and environmentally friendly method for reutilization of rare and precious metals in electronic waste. The main conclusions are as follows:
      (1) The work studied the enrichment of Pd(0) in waste PCBs with supercritical water oxidation (SCWO) and the deep degradation mechanisms of brominated epoxy resin. It was found that brominated epoxy resin in waste PCBs could be degraded into CnH2n+2, CO2, HO2 and NaBr in NaOH/H2O2 modified SCWO system. The results showed HO2• free radical generated by H2O2 caused the degradation of oxidized open ring of phenol, improving the oxidation of primary metal component Cu as well as the enrichment efficiency of Pd(0). By nucleophilic substitution and elimination reaction, NaOH improved debromination efficiency of brominated epoxy resin in SCWO as well as the transition from the main elements of Cu, Al and Ca to hydrates/chemical compounds. It also caused water gas shift reation and alkali silica reaction, improving the enrichment of Pd(0) from modified SCWO in different degrees.
      (2) The work studied SC-CO2 complexometric extraction of Pd(II) from multilayer ceramic capacitor and clarified coordination mechanism between Pd(II) and different kinds of complexing agents (Cyanex272, LIX84I and Cyanex302) in SC-CO2. It was found that the Pd(0) in waste capacitor can be extracted by acid leaching-extractant complexation. Mechanism studies showed the extraction efficiency of extractant Cyanex302 (with the central S atom) was much better than that of extractants Cyanex272 (with the central O atom) and LIX84I (with the central N atom). Molecular orbital theory showed Pd(II) could form π* with the S atom in Cyanex302, greatly enhancing stability and solubility of the formed Pd(II)-Cyanex302 in SC-CO2.
      (3) The work developed the process that SC-CO2 directly extracted Pd(0) from waste PCB. The results showed Pd(0) in the concentration with Pd, after combination with KI-I2, was converted to iodine complex anion [PdI3]ˉ by using oxidation and complexation. Then the charge attraction between [PdI3]ˉ and the cosolvent acetone could form the neutral complex [(CH3COCH3)nH][PdI3] that could be dissolved in SC-CO2. Without using acid as leaching reagents, Pd(0) can be converted to Pd(0), completing Pd(0) recovery with one step. Compared to the conventional recovery process of precious metals, it has the advantages such as simple recovery steps, less pollution, and without organic waste liquid by using SC-CO2 as solvent to recycle Pd(0) in waste PCBs.
      (4) The work developed sub/supercritical water co-treatment of spent LIBs and waste PVC. Using hydrochloric acid produced by dechlorination of PVC in subcritical/supercritical water as acid source, Li and Co were leached from lithium cobalt oxide of cathode material. Characterizations of XRD, SEM-EDS and GC-MS showed the organochlorine in waste PVC has been converted to inorganic Cl ligand of Li and Co after co-treatment in subcritical water. The waste PVC was synchronously converted to useful chemical materials, without the emission of organics containing Cl. The proposed co-treatment process provides a new recycling method and technology for harmless and resourceful treatment for spent LIBs and waste PVC.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36896
Appears in Collections:固体废弃物处理与资源化实验室_学位论文

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Recommended Citation:
刘康. 电子废弃物中稀贵金属的超临界流体回收方法与机理研究[D]. 北京. 中国科学院研究生院. 2016.
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