The ability of eelgrass (Zostera noltii (ZN)) to retain cupric ions from dilute aqueous solutions was studied as a function of pH, contact time and initial metal/sorbent ratio. Copper removal increased with pH, the optimum efficiency being attained between pH 5.5 and 6. When compared with other local lignocellulosic materials such as wood and corncob, Z. noltii appeared to be three times more effective than maritime pine and twice more than corncob. The presence of carboxyl groups in eelgrass was evidenced by infrared spectroscopy and photometric titration. These groups were found to participate in the adsorption process through cation exchange mechanisms, though other active binding sites were shown to be also involved. The metal and eelgrass relative concentrations appeared to influence the sorption capacity: the adsorption capacity of Z. noltii increased from 0.31 to 0.76 mmol Cu per gram as the metal/sorbent ratio increased. This behavior was partly explained by a change in the stoichiometry of a number of complexes as the metal and eelgrass relative concentrations varied. (C) 2003 Elsevier B.V. All rights reserved.