The geochemically-analogous process of metal recovery from second-hand resources via mechanochemistry: An atom-economic case study and its implications.

In the context of recycling metal to embrace the sustainability challenge, this work proposes a geochemically-analogous process of metal recovery through mechanochemistry for the first time, to avoid the limitations of on-going methods and to establish an innovative technology philosophy. This work systematically investigates this geochemically-analogous process, to keep it green and to generalize it further. Copper recovery from waste printed circuit boards (WPCBs), a typical copper-rich waste, is chosen as a case study in this work. Nearly 98% of the copper in the WPCBs can be recycled in the optimized conditions and 82.3% of the sulfur can be reused, by means of the process. Based on the experimental result, this paper purports a closed-loop route of copper recovery which follows the green chemistry principles (high yield, high atom economy and no secondary pollution). This route can be generalized into other second-hand resources that are rich in copper. Some other metals (e.g. lead) that are commonly present as corresponding sulfides in nature can be taken into consideration in this geochemically-analogous process as well.