Science Serving Maryland's Coasts

Alison M. (Straka) Zoll, The Catholic University of America

Class Year: 

Project Title: 

Sorption of the Rare Earth Elements on Ulva lactuca (Sea Lettuce)


The sorption of the rare earth elements (REEs) on Ulva lactuca (Sea Lettuce) was investigated at different ionic strengths over a wide range of pH values (4 - 8.5). REE concentrations were measured using an Inductively Coupled Plasma Mass Spectrometer (ICP-MS), and distribution coefficients (Ks) were calculated and plotted as a function of pH. In 0.5 M NaCl, the log(Ks) values are linear over the pH range 4 - 8.5. In 0.05 M NaCl, the log(Ks) values are linear from pH 4 5.5, followed by a sharp decrease and substantially decreased pH dependence between pH 6 - 8.5. Acid/base titration experiments were also conducted to determine the density of the functional groups on Ulva.
Additionally, Extended X-ray Absorption Fine Structure (EXAFS) was used to investigate the coordination chemistry of individual REE ions bound to functional groups on Ulva. This data was collected at Argonne National Laboratory (ANL) Advanced Photon Source in Argonne, IL.