FEASIBILITY STUDY FOR RECOVERING PRECIOUS METALS FROM E-WASTE

Printed circuit boards (PCBs) from electronic gadgets at the end of their useful life period are currently being dumped in landfills or incinerated, causing a serious environmental harm in the form of toxic gases or leached hazardous compounds. PCBs contain high amounts of precious metals; about 20 wt% copper, 0.04 wt% gold, 0.15 wt% silver, and 0.01 wt% palladium. The extraction of these metals from PCBs is both profitable and environmentally worthwhile. Hence, this study aims to design a commercial process to extract three of these metals, (copper, gold and silver) from PCBs of computers and mobile phones. The proposed extraction process has been divided into two stages: (1) physical separation, (2) metal recovery. Stage 1 involves size reduction followed by the corona electrostatic separator and the hydro-cyclone which separates metals from non-metals. Stage 2 separates individual target metals from each other by hydrometallurgical processing. This stage involves leaching and precipitation of the metals into their separate components. In a bid to develop an environmentally friendly technique for recovery of precious metals from electronic scrap, a critical comparison of main leaching methods is analyzed from both economic and environmental impact perspective. Experimental results have shown that cyanide leaching is the best leaching method for this research’s target precious metals from PCBs, on the basis of the economics, process applicability and recyclability.