The leaching of metals from waste printed circuit boards (WPCBs) in cupric chloride solutions (HCl-CuCl2-NaCl) was studied. Effects of initial concentration of cupric (8-157 mM Cu2+), chloride (0.7-2.0 M NaCl), temperature (20-80 degrees C), solids ratio (1-15 w/v) and air/oxygen (1 L/min) on the leaching of copper as well as other metals (i.e. Fe, Ni, Ag, Pd and Au) were investigated. The findings have shown that increasing the initial concentration of Cu2+ leads to a significant enhancement in the metal extractions. At Cu2+ concentrations of >= 79 mM, high extractions (i.e. >= 98%) for copper, nickel and iron were obtained over 120 min. An increase in the concentration of chloride (i.e. from 0.7 M to 2 M Cl-) decreased the extraction of copper by up to 40% at 60 min due to the decrease in the activity of free Cu2+. Rising the temperature from 20 degrees C to 80 degrees C resulted in a 1.38-fold increase in the copper extraction at 120 min. The activation energy (E-a) for leaching of copper was calculated to be approximate to 41 kJ/mol, indicative of a chemically controlled leaching reaction. Air/oxygen (1 L/min) was supplied for the regeneration of Cu2+, which improved the extraction of all the metals monitored. Increasing the solids ratio (1-15 w/v) adversely affected the leaching process with no copper extraction at 15 w/v. However, the extraction of metals (Cu, Ni, Ag and Pd) substantially ameliorated in the presence of oxygen. The current study have shown that copper, palladium, nickel and silver can be readily extracted from WPCBs in cupric chloride leaching where the extraction of gold is very limited. (C) 2014 Elsevier B.V. All rights reserved.