Main content area

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

Liu, Kang, Yang, Jiakuan, Hou, Huijie, Liang, Sha, Chen, Ye, Wang, Junxiong, Liu, Bingchuan, Xiao, Keke, Hu, Jingping, Deng, Huali
Environmental science & technology 2019 v.53 no.5 pp. 2748-2757
copper, copper sulfate, cost effectiveness, crystallization, cupric oxide, electronic equipment, electronic wastes, epoxides, fiberglass, forces, hydrogen, leaching, mechanochemistry, models, oxidants, oxidation, potassium persulfate, recycling, waste utilization
The recovery of copper (Cu⁰) 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 Cu⁰ recovery from WPCB powder is reported. Potassium persulfate (K₂S₂O₈), instead of acid/alkali reagents, was employed as the sole reagent in the cupric sulfate (CuSO₄) regeneration process. Complete oxidation of Cu⁰ in the WPCBs to copper oxide (CuO) and CuSO₄ was first achieved during mechanochemical processing with K₂S₂O₈ as the solid oxidant, and the K₂S₂O₈ was simultaneously converted to sulfate compounds [K₃H(SO₄)₂] via a solid–solid reaction with epoxy resin (CₙHₘOy) as the hydrogen donator under mechanical force. The rapid leaching of Cu species in the forms of CuO and CuSO₄ 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, CuSO₄·5H₂O was successfully separated by cooling crystallization of the hot saturated solution of sulfate salt [K₂Cu(SO₄)₂·6H₂O]. An efficient conversion of Cu⁰ to CuSO₄·5H₂O product, for WPCB recycling, was therefore established.