Heavy metal and A1 sorption capacities of Ca-loaded Laminaria japonica biomass were studied using equilibrium methodology. An evaluation of sorption performance and modeling in a two-metal system was carried out using a modified multi-component Langmuir isotherm. The maximum uptakes of Cr, Pb, Cu, Cd, Zn and Al calculated from the Langmuir isotherm were 1.81, 1.68, 1.59, 1.21, 0.87, and 2.79 mmoUg at pH 4.5, respectively. The interference of Al in heavy metal biosorptive uptakes was assessed by 'cutting' the three-dimensional uptake isotherm surfaces at constant second-metal final concentrations. The reduction of Pb, Cu, Cd, Zn and Cr uptakes at its final equilibrium concentrations of 1 mM at pH 4.5 was 77.7%, 80.4%, 86.0%, 89.1% and 50.1% on the presence of Al ion of I mM, respectively. The presence of Al ion greatly affected the uptake of all heavy metals tested except for Cr. (C) 2004 Elsevier Ltd. All rights reserved.