Comparative Life Cycle Analysis for Value Recovery of Precious Metals and Rare Earth Elements from Electronic Waste
thesisposted on 14.08.2019, 17:57 by Zhen Li
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
There is an ever-increasing concern regarding electronic waste (e-waste), which is the fastest growing waste stream in the world. E-waste contains highly toxic materials such as halogenated flame retardants and heavy metals, as well as precious metals like gold, silver, and platinum. Its proper management and disposition are paramount. Incentivized by various legislations and the intrinsic value of critical metals inside, recycling of e-waste is becoming an attractive business opportunity that also benefits the environment. A novel electrochemical recovery (ER) process has been developed as a promising alternative to the existing pyrometallurgical and hydrometallurgical processes-based technologies to recover base metals, precious metals, and rare earth elements (REEs) from e-waste. Experimental results indicate that the ER process has lower chemical consumption, enhanced control, and reduced energy demand compared to the pyrometallurgical and the hydrometallurgical processes. To quantify and compare the environmental performances of the three technologies, life cycle analysis has been conducted. The baseline comparison used $1000 revenue from the e-waste recovery as a functional unit. Results show that the ER process outperforms the other two processes in almost all impact categories adopted in TRACI and ILCD while there is no clear winner between the hydrometallurgical and the pyrometallurgical processes. The life cycle analysis helped identify the significant inputs for different processes. The highest impactful input for the ER method is hydrochloric acid, and for the pyrometallurgical method is copper scrap, while for the hydrometallurgical method, it is hydrogen peroxide, an oxidizer that accelerates base metal extraction process that dominates the overall environmental footprint. Other than the baseline case, the environmental impacts of recovering REE from e-waste with different processes and from other method were studied. The results indicate REE recovered from e-waste has a lower environmental footprint than virgin extraction. Overall, the ER process has the lowest impacts on the environmental side among the three e-waste treatment processes. The environmental viability of the ER process warrants the further development of the ER process at industrial scale.