In this work kinetic and equilibrium studies related to copper binding to the protonated macroalga Sargassum muticum are reported. An intraparticle-diffusion linear driving force (LDF) model has been chosen for the quantitative description of the kinetics at several initial metal concentrations. Copper intraparticle homogeneous diffusion coefficient (Dh) obtained is in the range 0.2–0.9 10 10 m2 s 1. NICA isotherm is demonstrated to constitute a substantial improvement with respect to a simpler Langmuir competitive equation. The binding parameters were chosen to provide the best simultaneous description of the equilibrium experiments. Values of log eK Cu (4.3), nCu (1) and p (0.31) in NICA isotherm, and log KCu (3.5–5) in Langmuir competitive model, have been obtained. These parameters have been also used to predict the competition between copper and cadmium for binding sites. Two acids, HNO3 and HCl, have been tested to evaluate their effectiveness to release copper from the metal-laden biomass. ; This work was funded by the projects CTM2006-03142/TECNO (from the Ministerio de Educación y Ciencia of Spain) and PGDIT06- TAM00401CT (from Xunta de Galicia). The authors would like to thank Dr. I. Bárbara and Dr. J. Cremades (University of A Coruña) for the collection and classification of the algae species. Pablo Lodeiro gratefully acknowledges financial support through Ángeles Alvariño project AA 10.02.56B.444.0 and the grant for research stay outside Galicia 10.02.561B.480.0 (from Xunta de Galicia), both co-funded by 80% with European Social Funds.