The present work describes the preparation of new chelating materials derived from Posidonia for adsorption of heavy metal ions and dye in aqueous solution. The first part of this report deals with the chemical modification of Posidonia with succinic anhydride. Thus, we have obtained materials with various succinyl groups contents (from 29.8 to 39.2%). The obtained materials were characterized by infrared and CP/MAS C-13-RMN spectroscopy. The rate of succinyl content of the modified Posidonia was determined by saponification. The second part is devoted to the evaluation of the adsorption capacity of metal ions such as Pb2+ and dye such as direct red 75 (DR75) for raw and modified Posidonia materials. Two possible ways for the adsorption of these pollutants are studied: adsorption of each pollutant alone onto these supports, and cumulative adsorption of both metal ions and dye on the same supports. In the last case, the pollutant is adsorbed successively from two different solutions. The effects of pollutants concentration, support dose, pH, contact time and temperature on adsorption of each pollutant were evaluated. The results showed that the raw and modified Posidonia show a high capacity for Pb2+ adsorption. The capacity of modified Posidonia saturated with Pb2+ to adsorb DR75 was found 147.12 mg g(-1). While the adsorption capacity of the nonsaturated modified Posidonia was equal to 81.63 mg g(-1). The pseudo-second-order model was the best to represent adsorption kinetics of DR75. The pseudo-first-order model would be better for fitting the adsorption kinetic process of Pb2+ onto raw and modified Posidonia. The adsorption isotherms of Pb2+ could be described by the Jossens equation model. Any of the tested models can describe the adsorption of DR75 onto the studied materials. These results confirm that the adsorption of DR75 from aqueous solution was multilayer. (C) 2009 Elsevier B.V. All rights reserved.