Supergravity-enhanced liquation crystallization for metal recovery from waste printed circuit boards

Abstract

Waste printed circuit boards (WPCBs) present serious threats to the environment but also the opportunity to recover the valuable metals, motivating a search for processes to allow their cost-effective recycling. In this regard, the advantages afforded by liquation crystallization and supergravity technology were combined herein to develop a new supergravity-enhanced liquation crystallization process for recovering metals from WPCBs. The WPCB particles were fully smelted to obtain WPCB alloy. Fe-rich, Cu–Zn, Cu–Sn, and Pb-rich phases were progressively precipitated from the alloy melt as the temperature decreased and subsequently stratified from top to bottom after supergravity-induced enrichment owing to their different densities. Fe-rich, Cu–Zn, Cu–Sn, and Pb-rich alloys were obtained via supergravity-assisted separation at 1100, 850, and 500 °C, respectively. The mass fractions of Fe in the Fe-rich alloy, (Cu + Zn) in the Cu–Zn alloy, (Cu + Sn) in the Cu–Sn alloy, and Pb in the Pb-rich alloy reached 81.8 wt.%, 92.9 wt.%, 91.2 wt.%, and 94.6 wt.%, respectively, in the three separation steps. The final recoveries of Fe, Cu, Zn, Sn, and Pb after three supergravity-assisted separation stages reached 98.8%, 97.8%, 94.1%, 96.9%, and 97.4%, respectively. This study demonstrates an efficient method for separating metals from WPCBs and improving the grade of the separated metals.