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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.