Powdered activated carbons (PACs) were produced from oil palm empty fruit bunches (EFB) by varying the operating parameters of temperatures, CO2 gas flow rates and activation times using 2-level full factorial experimental design. The EFB samples were first carbonized for 30 min using nitrogen gas followed by physical activation using CO2 to optimize best production conditions. The optimum conditions for PACs produced were investigated through adsorption tests on aqueous solution of phenol. The results of this study demonstrated that the activation temperature with the range of 800-900 degrees C had the most significant effect on the adsorption characteristics as well as the yield of the activated carbon produced. Based on the analysis of variance (ANOVA) and model equation developed, the optimum production conditions for the EFB PAC were found to be at the activation temperature of 900 degrees C with CO2 gas flow rate of 0.1 L/min and activation time of 15 min. Characterization of PAC produced showed that the activation conditions would find good-quality adsorbent with the BTE surface area of 345.1 m(2)/g and well forming pores distribution. (C) 2009 Elsevier B.V. All rights reserved.