Two series of activated carbons were prepared from Spartina alterniflora and from its anaerobically digested residue by H3PO4 activation at various process conditions, and used as adsorbents for the removal of cadmium (II) in aqueous solutions. The surface areas and pore volumes of carbons were derived from adsorption isotherms (N-2 at 77 K). The surface chemistry of carbons was investigated by infrared spectroscopy. Comparison study indicated that physicochemical properties of the activated carbons were strongly dependent not only on activation conditions but also on biopolymer contents of precursors. Several isotherm models were investigated and the adsorption isotherm data were best represented by the Langmuir isotherm model, with a maximum monolayer adsorption capacity of 47.85 mg/g at 25 degrees C. The results showed that the activated carbon produced from S. alterniflora could be employed as a promising adsorbent for removing cadmium (II) from aqueous solutions. (C) 2011 Elsevier B.V. All rights reserved.