Activated carbons are prepared from cotton stalks by chemical activation with ZnCl2, H2SO4 and physical activation using CO2 and steam-CO2 mixture for temperatures 01 750, 850 and 900 degrees C. The effects of activation temperature and duration time, impregnation concentration of agent, impregnation times, and physical activating agent are examined. These materials are characterized by adsorption/desorption of N-2 to determine the BET areas, thermogravimetric analysis (TG, DTA), FTIR and scanning electron microscopy (SEM). ZnCl2 under CO2 atmosphere was found more effective than H2SO4 as a chemical reagent under identical conditions in terms of porosity development. The maximum BET surface area is found to be 2053 m(2)/g for active carbons produced with ZnCl2 activation under CO2 atmosphere. (C) 2011 Elsevier B.V. All rights reserved.