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The recovery of various metals from waste materials is an important issue in order to conserve the environment and metal resources. Copper is used for cables, electric appliances, etc., and is a very important material for industries in now and the future. A printed circuit board (PCB) also contains copper in addition to many kinds of valuable metals such as gold, silver, palladium, nickel and so on. The copper content in the PCB is 10 to 30 mass%, which is the highest among the metallic elements. There are two ways to recover copper, either pyrometallurgically or hydrometallurgically. Hydrometallurgical treatments generally have more flexibilities during the process scale and control. Sulfuric and hydrochloric acid solutions are often employed as leaching agents in the hydrometallurgical treatment; however, in these cases, the separation processes tend to become complicated because of the poor selectivity during the leaching. It has been reported that certain kinds of complexing agents are effective for selective leaching. 1–6) Majima et al. reported the selective leaching of copper from motor scraps using cupric ammine solutions. 1, 2) Zhou et al. studied the removal of copper from ferrous scrap by an ammonia leaching method. 3, 4) In these studies, Cu (I) ions were obtained under an air or oxygen atmosphere as the reaction product, and then metallic copper would be electrowon from a sulfuric acid solution obtained by solvent extractionstripping. During this electrowinning, one mole of copper deposition at the cathode requires two moles of electrons, and oxygen is evolved at the anode. Its power consumption is 2000 to 2500kWhtonĀ1. 7) In …