Separating and recycling metal mixture of pyrolyzed waste printed circuit boards by a combined method

• Published in: Waste management (Elmsford) Vol. 107; pp. 113 - 120
• Main Authors: Chen, Bin, He, Jie, Sun, Xiaojun, Zhao, Jiuzhou, Jiang, Hongxiang, Zhang, Lili
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 15.04.2020
• Subjects: aluminum; Cell Phone; chromium; Copper; electronic equipment; Electronic Waste; electronic wastes; energy; Environmental Pollution; environmental protection; gold; iron; lead; Liquid-liquid phase separation; Low-temperature alkaline smelting; Metal recycling; Metals; mobile telephones; nickel; Noble metals; pollution; pyrolysis; Recycling; separation; silicon; silver; sustainable development; tin; toxic substances; Waste printed circuit boards; zinc; Waste printed circuit boards; Liquid-liquid phase separation; Noble metals; Metal recycling; Low-temperature alkaline smelting
• ISSN: 0956-053X; 1879-2456; 1879-2456
• DOI: 10.1016/j.wasman.2020.04.006

[Display omitted] •A combined process is developed for treatment and recovery of metal mixture in WPCBs.•Liquid-liquid phase separation is used for metal enrichment.•Amphoteric metals are separated by low-temperature alkaline smelting.•Noble metals gold and silver are efficiently enriched to form a high-value group. Waste printed circuit boards (WPCBs) contain a variety of valuable and hazardous materials. Recycling WPCBs is an important subject not only for environmental protection but also for sustainable development of resources. In this work, a new method combined low-temperature alkaline smelting with liquid-liquid phase separation is proposed to separate and recycle metal mixture in pyrolysis residue of WPCBs of mobile phones. During the low-temperature alkaline smelting process, amphoteric metals Al, Pb, Si, Sn, and Zn are firstly separated and recycled from the metal mixture with the separation rates of 99.5%, 81.6%, 97.8%, 88.4% and 95.7%, respectively. To separate the remaining metal mixture mainly containing elements Cu, Fe, Cr, Ni, Au and Ag, a liquid-liquid phase separation system is designed. As a result, the noble metals Au and Ag are concentrated in the copper-rich substance to form a high-value group, while the elements Ni and Cr distribute in the iron-rich substance. The iron-rich substance can be reused in the liquid-liquid phase separation process. In the super-gravity field, the recycling rates of the metals Au, Ag, Cr and Ni reach 98.1%, 99.8%, 95.6% and 75.4%, respectively. Furthermore, the iron-rich substance can be reused back to the liquid-liquid separation system. The copper-rich substance enriched by the noble metals can be efficiently recovered with low energy consumption and less pollution. This work provides an environmentally friendly and efficient route for separating and recycling the metal mixture in WPCBs.