The biosorption of copper(II) by the marine alga Sargassum sp. was investigated in a batch reactor and in a fixed-bed column (temperature = 30 degreesC; pH 3.5). Langmuir and Freundlich sorption models were used to represent the equilibrium data. Experimental breakthrough curves in a fixed-bed column were obtained with a flow rate of 6 ml/min and feed concentration of 1, 2, 3 and 6 meq/l. A model that describes the dynamics of copper(II) ion sorption in the column was obtained from the mass balance in the fluid phase and the biosorbent. According to mass transfer three equations are available to represent the rate of adsorption. The model parameters: mass transfer coefficients, axial dispersion coefficients and constants of the kinetic equation, had their values adjusted from the experimental breakthrough curves. The model in which the mass transfer is controlled by diffusion in the biosorbent best represented the fixed-bed column dynamics. (C) 2002 Elsevier Science Ltd. All rights reserved.385791799