Facile and Cost-Effective Approach for Copper Recovery from Waste Printed Circuit Boards via a Sequential Mechanochemical/Leaching/Recrystallization Process.

The recovery of copper (Cu) from waste printed circuit boards (WPCBs) is a great challenge as a result of its heterogeneous structural properties, with a mixture of metals, epoxy resin, and fiberglass. In this study, a three-step sequential process, including mechanochemical processing, water leaching, and recrystallization, for Cu recovery from WPCB powder is reported. Potassium persulfate (KSO), instead of acid/alkali reagents, was employed as the sole reagent in the cupric sulfate (CuSO) regeneration process. Complete oxidation of Cu in the WPCBs to copper oxide (CuO) and CuSO was first achieved during mechanochemical processing with KSO as the solid oxidant, and the KSO was simultaneously converted to sulfate compounds [KH(SO)] via a solid-solid reaction with epoxy resin (C H O ) as the hydrogen donator under mechanical force. The rapid leaching of Cu species in the forms of CuO and CuSO was therefore easily realized with pure water as a nontoxic leaching reagent. The kinetics of the leaching process of Cu species was confirmed to follow the shrinking nucleus model controlled by solid-film diffusion. Finally, CuSO·5HO was successfully separated by cooling crystallization of the hot saturated solution of sulfate salt [KCu(SO)·6HO]. An efficient conversion of Cu to CuSO·5HO product, for WPCB recycling, was therefore established.