Fractionation of Platinum Group Elements in Aqueous Systems:  Comparative Kinetics of Palladium and Platinum Removal from Seawater by Ulva lactuca L

A marine macroalga, Ulva lactuca L., was used as a substrate to compare the kinetics of palladium (Pd) and platinum (Pt) removal from seawater. This work indicates that, while the equilibrium behaviors of Pd and Pt are in many respects similar, their kinetic behaviors are quite distinct. The removal of both Pt(II) and Pt(IV) from seawater by U. lactuca is slower than the removal of Pd(II) by approximately an order of magnitude. Relative Pd and Pt removal rates are strongly influenced by system hydrodynamics. Under quiescent conditions, λ(Pd)/λ(Pt), the ratio of Pd and Pt removal rates, is 7 ± 2, whereas under turbulent conditions λ(Pd)/λ(Pt) can be as large as 27. These observations suggest that the disparate kinetic behaviors of Pd and Pt may produce considerable differences in the environmental dispersion of these elements.