The removal of organic species from aqueous solution by activated carbons is investigated. The latter ones are prepared from olive husks and almond shells. A wide range of surface area values are obtained varying temperature and duration of both carbonization and activation steps. The adsorption isotherm of phenol, catechol and 2,6-dichlorophenol involving the activated carbons prepared are obtained at 25degreesC. The corresponding behavior is quantitatively correlated using classical isotherm, whose parameters are estimated by fitting the equilibrium data. A two component isotherm (phenol / 2,6-dichlorophenol) is determined in order to test activated carbon behavior during competitive adsorption.