In,this work, adsorption of copper(II) ions on alga has been studied by using batch adsorption techniques. The equilibrium biosorption level was determined as a function of contact time at several initial metal ion concentrations. The effect of adsorbent concentration on the amount adsorbed was also investigated. The experimental adsorption data were fitted to the Langmuir adsorption model. The free energy change (DeltaG(0)) for the adsorption process was found to be -12.60 kJ/mol. The results indicated that the biomass of Ulothrix zonala is a suitable biosorbent for both the removal and recovery of heavy metals from wastewater. (C) 2002 Elsevier Science Ltd. All rights reserved.