Abstract
This paper presents an experimentally-proved hydrometallurgical process for selective metals recovery from the waste-printed circuit boards (WPCBs) using a combination of conventional and time-saving methods: leaching, cementation, precipitation, reduction and electrowinning. According to the results obtained in the laboratory tests, 92.4% Cu, 98.5% Pb, 96.8% Ag and over 99% Au could be selectively leached and recovered using mineral acids: sulfuric, nitric and aqua regia. Problematic tin recovery was addressed with comprehensive theoretical and experimental work, so 55.4% of Sn could be recovered through the novel physical method, which consists of two-step phase separation. Based on the results, an integral hydrometallurgical route for selective base and precious metals recovery though consecutive steps, (i) Cu, (ii) Sn, (iii) Pb and Ag, and (iv) Au, was developed. The route was tested at scaled-up laboratory level, confirming feasibility of the process and efficiencies of metals recovery. According to the obtained results, the proposed hydrometallurgical route represents an innovative and promising method for selective metals recovery from WPCBs, particularly applicable in small scale hydrometallurgical environments, focused on medium and high grade WPCBs recycling.
Highlights
Due to high concentrations of the base and precious metals and their corresponding values, waste printed circuit boards (WPCBs) represent the most significant part of electronic waste
Chemical composition composition and material morphology analyzed by X‐ray diffraction (XRD) and of pregnant leaching solutions (PLS) and was solutions after metals recovery (MRS)analysis was determined by scanning electron microscopy (SEM)
°C forsamples, 1 h) in of waste-printed circuit boards (WPCBs) was determined after thermal treatment of three which organic fraction was burned, oxides together with other slag‐forming each weighing 1.00 kg, in medium induction furnace in which compounds werewas transferred to slag phase, and metals were collected in melt (M° state)
Summary
Due to high concentrations of the base and precious metals and their corresponding values, waste printed circuit boards (WPCBs) represent the most significant part of electronic waste. WPCBs recycling is integrated in the base metals production process in which valuable metals are concentrated in the metal carrier, copper or lead, and subsequently valorized through series of pyro-hydro-electro refining operations to produce high-purity metals [3,4]. These operations are well-established on the industrial scale, intense marketing activities hinder environmental risks, and their ecological acceptance is dependent on implementation of high-efficient. Metals 2018, 8, x FOR PEER REVIEW multi-step processing route tested at scaled-up laboratory level, confirming the Materialshydrometallurgical and Methods process feasibility and the metals recovery efficiencies
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