To convert the hazardous oily sludge into high quality activated carbon for water pollutant adsorption, a new preparing procedure has been proposed in current study by adding a de-oiling step before activation. The pore structure and surface chemistry of produced active carbons (ACs) were characterized by scanning electron microscopy, N-2 adsorption-desorption, XRD, FTIR and XPS. Due to the high content of asphaltene, oily sludge is a promising material for activated carbon production. The surface area of the activated carbon prepared with the proposed de-oiling step was 3292 m(2)/g which was two times higher than that of normally prepared AC. Moreover, by applying the de-oiling step, the methylene blue adsorption capacities significantly increased from 17.8 mL/0.1 g to 64.6 mL/0.1 g reaching that of ACs generated from commercial asphalt. Moreover, the heavy metal leaching values of the ACs prepared were far below that of hazardous materials. Therefore, the oily sludge could be promising raw material for activated carbon production and the de-oiling procedure could improve the quality of ACs significantly. (C) 2017 Elsevier B.V. All rights reserved.