Extraction of copper and the co-leaching behaviour of other metals from waste printed circuit boards using alkaline glycine solutions

Waste printed circuit boards (WPCBs) are a complicated and valuable fraction of electric and electronic waste. The recycling of them is critical to avoid environmental pollutions and to reuse resources. In particular, the e-waste import bans have been implemented in many traditional waste-importing countries in recent years, which is making the sustainable recycling essential and crucial for the advanced economies. In this study, a sustainable approach using alkaline glycine solution for the extraction of copper (Cu) from WPCBs, and the leaching behaviour of other metals (Ni, Al, Fe, Pb, Sn, Co, Zn, Au, Ag and Pd) is presented. Various leaching parameters, including initial pH, glycine concentration, solid content, oxidant, particle size, temperature and time were investigated. A maximum Cu extraction of 96.5 % was achieved, with high co-extraction of base metals (BMs). The extraction of BMs was dependent on the pH of leaching solution, which was highly correlated with other variables. BMs extraction was largely influenced by glycine concentration and solid content, while the sensitivity to H2O2, temperature, and particle size was insignificant. SEM-EDS analysis of leaching residue indicated that the unleached Cu may be locked in inert layers, e.g. Sn/solder materials. The kinetic analysis showed that the extraction of Cu from WPCBs (100 % < 2 mm) at room temperature with ambient O-2 in air as an oxidant was mainly controlled by internal diffusion.