Activated carbons have been prepared by a two-step physical activation with steam at different burn-off levels to study the porosity development and its effect in zinc adsorption from aqueous solutions. The plain material used was the residual from the extraction with solvent of the kernel-oil [solvent extracted olive pulp (SEOP)]. Olive, apricot and peach stone have been also used as different precursors. The products were characterized by N-2 at 77 K adsorption, Hg porosimetry and iodine number determination. The influence of surface complexes and pH has been investigated in an attempt to elucidate the adsorption phenomena. The effect of different treatments [demineralization with H2SO4 and oxidation with (NH4)(2)S2O8] was also evaluated for the adsorption of zinc species. Both basic and acidic carbons, originated from SEOP, show remarkable adsorption ability at solution pH = 7. Their adsorption ability mainly depends on the content and nature of functional surface groups, the ash content of the precursors and the pH of the solution. These activated carbons were proved to be efficient adsorbents for the removal of water pollutants and contaminants. (C) 2002 Elsevier Science B.V. All rights reserved.