The binary adsorption of Cu(2+)-Cd(2+), Pb(2+)-Cd(2+) and Pb(2+)-Cu(2+) mixtures onto Ca-Alginate beads, prepared from Laminaria digitata, was studied using batch experiments. Competitive sorption models including extended Sips, extended Langmuir, Jain and Snoeyink modified Langmuir (JS modified) as well as Ideal Adsorpted Solution Theory (IAST) models were applied to predict the binary adsorption using single component adsorption parameters. The extended and the JS modified Langmuir approaches provide excellent prediction of the binary adsorption, while the extended Sips fails to predict the experimental data, giving only fair results in the case on Pb(2+)-Cu(2+) mixtures. On the contrary, the IAST models, though they are more complicated, provide less accurate estimation of sorption in binary metal ion solutions. In general, single component adsorption parameters can be effectively used for the prediction of a materials adsorption performance in binary metal ion solutions.