Biosorption of the lanthanides: Lanthanum (La3+), Europium (Eu3+) and Ytterbium (Yb3+) from single-component and multi-component batch systems using Sargassum polycystum Ca-loaded biomass was studied. The ion exchange sorption mechanism was confirmed by the release of calcium ions from the biomass that matched the total number of metal and protons removed from the solution. The metal binding increased with pH due to the decrease of proton concentration in the system, as they also compete for the binding sites. The maximum metal uptake capacity for pH 3, 4 and 5 ranged approximately between (0.8-0.9) mmol g(-1) for La (0.8-0.9) mmol g(-1) for Eu, and (0.7-0.9) mmol g(-1) for Yb. Biosorption from multi-component mixtures was examined at pH 4 using equimolar initial concentrations of the metals. The metal affinity sequence established was Eu > La > Yb, and the maximum metal uptake obtained was 0.29, 0.41, 0.28 mmol g(-1) for La, Eu and Yb, respectively. (C) 2004 Elsevier Ltd. All rights reserved.
