Oxidation leaching copper from metal powders of waste printed circuit boards (PCBs) was conducted at room temperature in sulfuric acid solution. The result showed that the copper in metal powders was oxidized by Cu2+ to form CuCl2- in the presence of chloride ion without electrochemical oxidation. Then, CuCl2- was oxidized into CuSO4 by oxygen derived from the air insufflated into leaching solution. The leaching rate of copper reached 100%. The whole reaction took 5.5 h because it was limited by the low solubility of the air in water. In the electro-oxidation conditions, the chloride ion was electro-oxidized into ClO-, which oxidized CuCl2- into CuSO4 and ClO- was reduced into Cl- itself again at the same time. Since Cl- was recycled in the solution not only as a complexing agent but also as an oxidant, which made the reaction speed up to 3.5 h to reach 100% leaching rate. Leaching solution was concentrated to crystallize CuSO4.5H(2)O, and crystal liquor was reused to leach copper from metal powders. (C) 2008 Elsevier B.V. All rights reserved.