In this work, an effective and size-controlled process for preparing Cu2O nanomaterials from waste PCBs by supercritical water (SCW) combined with electrokinetic (EK) technique was developed. SCW was used for the pretreatment of waste PCBs, and highly uniform and monodisperse Cu2O nanoparticles with different sizes were prepared successfully from waste PCBs in EK process. Cu2O nanoparticles with average sizes of 5, 11, 25 and 40 nm could be prepared in the presence of nanoparticles stabilizer (PVP) with the concentrations of 40, 30,20 and 10 g/L, respectively. The average size of Cu2O nanoparticles decreased from 49.5 to 18.2 nm when current density increased from 10 to 20 mA/cm(2), and the size uniformity of nanoparticles was improved distinctly at a higher current density. The size of Cu2O nanoparticles increased with the increase of EK time, and agglomeration of particles was observed after 8 h EK reaction. Up to 90 wt% of the Cu in waste PCBs could be recovered as Cu2O nanoparticles under optimized condition. It is believed that the process developed in this study is simple and practical for size-controlled preparation of nanomaterials from waste PCBs or other Cu-rich solid wastes. (C) 2012 Elsevier B.V. All rights reserved.