Adsorption of lead and copper ions by algae Gelidium and algal composite material was studied in a continuous stirred tank adsorber (CSTR). Danckwerts curves show that dead volumes and by-passes do not exist inside the reactor. The average residence time for cadmium ions was tau = 15.2 +/- 0.2 min, and the useful adsorber volume V-r = 540 cm(3). Varying stirring velocity in the range 100-270 rpm the breakthrough curves show that a resistance to the mass transfer exists in the film of fluid around particles. The analysis of the effect of the flow rate on the breakthrough curves leads to the conclusion that the curves sharpness increases with flow rate. As expected, the larger the initial lead concentration, the faster the breakthrough of the metal, as the binding sites became more quickly saturated. The slope of the breakthrough curve increases when increasing the influent concentration. For higher initial pH values, the breakthrough time increases since metal uptake capacity increases. Biosorbents regeneration can be achieved by metal ions desorption with nitric acid as eluant. Desorption is an ion exchange process between metal ions loaded in the biomass and H+ ions in the solution. Two mass transfer models were developed to simulate biosorption and desorption performances. These models were able to predict the experimental results in a quite good manner. (C) 2007 Elsevier B.V. All rights reserved.