Lead collection after automatic components removal from printed circuit boards as a “novel” process for noble metals recovery from WEEE

Abstract

In recent years, the recovery of noble metals from WEEE (Waste Electrical and Electronics Equipment) has received great attention in the academic and industrial community since it highly contributes to decrease the cost of the recycling and/or disposing of the short life cycle of electronic devices. Noble metals are mainly present in Printed Circuit Boards (PCBs) which are normally sold in bulk to specialized companies or sent to “recycling sites” where they may be open burned creating a great environmental concern. An alternate route is to further subject the PCB to a manual or automatic dismantling of the integrated circuits and chips. After a study conducted on more than 20.000 kg of WEEE, it has been shown that easily removable parts will account for 13,01% of the PCB w/w (0,75% of the whole sample) but will contain 89,50% of gold (2109 ppm). Since the removed parts are low in weight but highly enriched, lead collection could become a viable process for noble metal recovery. The main components of the above parts are the Silicon wafers. Since no bibliographic information is available on this kind of “gold matrix” the aim of the present study has been to assess the best quantity of the flux primary components (litharge, sodium bicarbonate, anhydrous borax) to enhance gold recovery. Results greater than 90% have been assessed.