title: Selective leaching of valuable metals from waste printed circuit boards.
abstract: This study was carried out to recover valuable metals from the printed circuit boards (PCBs) of waste computers. PCB samples were crushed to smaller than 1 mm by a shredder and initially separated into 30% conducting and 70% nonconducting materials by an electrostatic separator. The conducting materials, which contained the valuable metals, were then used as the feed material for magnetic separation, where it was found that 42% of the conducting materials were magnetic and 58% were nonmagnetic. Leaching of the nonmagnetic component using 2 M H2SO4 and 0.2 M H2O2 at 85 degrees C for 12 hr resulted in greater than 95% extraction of Cu, Fe, Zn, Ni, and Al. Au and Ag were extracted at 40 degrees C with a leaching solution of 0.2 M (NH4)2S2O3, 0.02 M CuSO4, and 0.4 M NH4OH, which resulted in recovery of more than 95% of the Au within 48 hr and 100% of the Ag within 24 hr. The residues were next reacted with a 2 M NaCl solution to leach out Pb, which took place within 2 hr at room temperature.
authors.affiliation: Korea Chemical Co., Kwangju, Korea.
authors.forename: Chi Jung
authors.initials: CJ
authors.lastname: Oh
authors.forename: Sung Oh
authors.initials: SO
authors.lastname: Lee
authors.forename: Hyung Sik
authors.initials: HS
authors.lastname: Yang
authors.forename: Tae Jun
authors.initials: TJ
authors.lastname: Ha
authors.forename: Myong Jun
authors.initials: MJ
authors.lastname: Kim
mesh_terms: D003201:Computers; D003247:Conservation of Natural Resources; D004581:Electronics; D008670:Metals; D011640:Public Policy; D012037:Refuse Disposal
chemical_list: D008670:Metals