Electronic waste treatment: Part 1. Autoclave oxidation–leaching using pyrite waste from mine tailing

A process to co-treat electronic and pyrite (FeS2) wastes in an autoclave (high pressure and temperature) under oxygen gas atmosphere for extraction of metals from electronic waste was investigated in this study. The electronic waste sample contained high Cu (13–20%), Au (230–360 g/t), Ag (480–1020 g/t), including Pt, Pd and Ni among many other metals. Pyrite samples obtained as mine tailings for the study contained 69.1% FeS2 (32.5% Fe and 36.6% S) and was used as sulfur source for the generation of H2SO4 during autoclave oxidation to subsequently extract Cu and other base metals in the electronic waste. Reaction temperature and time, autoclave pressure, pulp density and H2SO4 concentration were investigated to evaluate metals extraction. At temperatures ranging from 120 to 180 °C and autoclave pressure of 2 MPa, pyrite was completely oxidized. Subsequently, Cu extraction reached over 99% and very high extraction of Zn, Ni and Cr metals was achieved within 1 h. The solid products from autoclave oxidation containing precious metals (Au, Ag, Pt, Pd) can be treated separately for their recovery.