ADSORPTION OF TRIVALENT LANTHANIDES AND ACTINIDES BY MARINE SEDIMENTS

Knowledge of the chemical behavior of (radio)toxic elements in natural/environmental systems is of fundamental importance for the performance of environmental impact assessments and the application of protection measures after possible contamination. The interaction of actinides with marine sediments is of particular interest because marine sediments constitute the final receptors of the majority of actinides (Th, Am, Pu). In order to study the chemistry of trivalent actinides (e.g. Am(III), Cm(III)) often trivalent lanthanides are used as analogues, because lanthanides in aqueous solutions are generally stable in the trivalent oxidation state, present similar chemical behaviour as trivalent actinides, are non-radioactive and posses useful spectroscopic/fluorescent properties. In this study we have investigated the interaction of Nd(III) with two different types of marine sediments as a function of different parameters (e.g. pH, [Nd(III)](o), I, tcontact) to evaluate their effect and get more information on the adsorption of Nd(III) by marine sediments. In this context, the effect of the particle coating with NOM (e.g humic acid) on the adsorption properties of the sediment samples has also been studied. According to the experimental results the adsorption of Nd(III) ions by marine sediments is (a) a relatively fast process (b) the adsorption data are well described by the Langmuir isotherm and (c) the adsorption properties (e.g. adsorption capacity, pH and ionic strength effects) of the different sediment types differ significantly from one another, depending on the (surface) composition.