Green chemistry for precious metals recovery from WEEE

Hydrometallurgical methods for precious metal (PM) recovery from complex matrices, such as waste, have been mostly inherited from the well-known processes conventionally applied to ores and jewelry ashes: despite the risks related to their use, cyanidation and aqua-regia leaching remain the most widely used chemical processes for PM dissolution and recovery on an industrial scale in the case of waste electrical and electronic equipment. This is mainly due to the effectiveness of these reagents in PM dissolution and the common awareness that these metals, showing high reduction potential and lower reactivity with respect to most elements, seem to require aggressive reactants in order to obtain effective metal dissolution. In this chapter, the peculiar contribution of coordination and green chemistry in designing new safer reagents and processes for effective and selective metal dissolution and recovery, will be discussed, highlighting the state-of-the-art on promising effective sustainable lixiviants and the future perspectives of these early-stage multidisciplinary studies.