Eco-friendly and cost-effective strategies for metals recovery from printed circuit boards

The possible optimization of metal recovery from Printed Circuit Boards (PCBs)and Central Processing Units (CPUs)has been investigated. Usual practice is to recover primarily the metals with the highest market price. In contrast, the present work shows how strategic considerations of the value share (%)of metals content and data regarding the environmental impact of their recovery can instruct about the best strategies to adopt, pointing at the metals to be recovered as a priority depending on the case. An accurate PCBs’ characterization carried out through microwave digestion with a mixture of HNO3, HF and HCl, is a first essential step of the procedure. Then, metals are recovered through chemical leaching with different chemical substances, exploiting both chemical and physical steps. A proposal is presented to improve the environmental and economic sustainability of the treatment of PCBs, which provides for the initial recovery of Cu, Pb and Sn from the whole boards, through leaching with 6M HNO3, followed by the recovery of gold and other precious metals from the board components once removed and appropriately crushed. Although unusual, the recovery procedure can be adapted accordingly, allowing greater profits, easier management and higher metals recovery rates