The main objective of this work is to prepare and characterize activated carbon form oil palm fiber (PFAC), an industrial solid waste abundantly available from the biodiesel manufacturing plants, via microwave assisted KOH activation. The influences of chemical impregnation ratio (0.25-2.00), microwave power (90-800 W) and radiation time (2-8 min) on the properties of activated carbon were investigated. The adsorptive behavior of PFAC was quantified using methylene blue (MB) as dye model compound, while the surface chemistry was characterized by determination of surface acidity/basicity, Fourier transform infrared spectroscopy and zeta potential measurement. Equilibrium data were examined using a comparison of linear and non-linear isotherm models. The optimum conditions resulted in PFAC with a monolayer adsorption capacity of 382.32 mg/g for MB and carbon yield of 32.09%. The BET surface area, Langmuir surface area and total pore volume were determined to be 1223 m(2)/g, 1827 m(2)/g and 0.72 cm(3)/g, respectively. The adsorption kinetic was well fitted to the pseudo-second-order model. (c) 2012 Elsevier B.V. All rights reserved.