Metals recovery from printed circuit boards: the pursuit of environmental and economic sustainability

The possible optimization of metal recovery from Printed Circuit Boards (PCBs) and Central Processing Units (CPUs) has been investigated. Usual practice is to primarily recover 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. In particular, a proposal to improve environmental and economic sustainability of the PCBs’ treatment is presented, which contrary to expectations first considers the recovery of Cu, Pb and Sn by leaching with 6M HNO3, followed only later by the recovery of gold and other precious metals. Although unusual, the recovery procedure can be adapted accordingly, allowing more profits, easier management and higher metals recovery rates.