Waste printed circuit boards (PCBs) are used as precursor for activated carbons preparation by three ways, that is, AC-H3PO4 is prepared by phosphoric acid activation; AC-H3PO4-Steam is prepared by the steam reactivation to AC-H3PO4, and AC-H3PO4/Steam is prepared by impregnation with phosphoric acid followed by steam. The activated carbons obtained under optimum conditions were characterized using N-2 adsorption/desorption isotherms, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Batch adsorption studies were performed to evaluate the adsorption properties of the three adsorbents toward malachite green (MG). Compared with AC-H3PO4, AC-H3PO4-Steam has higher BET surface area (S-BET) and microspores content, and less functional groups, indicating steam reactivation has an obvious advantage in improving the physical structure, chemical properties and adsorption capacities of activated carbons. While AC-H3PO4/Steam showed higher yield, lower SBET, more functional groups and higher adsorption capacities for malachite green than that of AC-H3PO4-Steam. For the three adsorbents, the adsorption kinetics followed the pseudo-second-order model. Adsorption experiments indicated that adsorption data fitted the Langmuir equation best than Freundlich and Dubinin-Radushkevich (D-R) models for AC-H3PO4, AC-H3PO4-Steam and AC-H3PO4/Steam. The adsorption has been confirmed to be an endothermic and spontaneous process through the thermodynamic parameters. (C) 2014 Elsevier B.V. All rights reserved.