title: Sorption and redox speciation of plutonium at the illite surface under highly saline conditions.
abstract: Natural groundwater may contain high salt concentrations, such as those occurring at several potential deep geological nuclear waste repository sites. Actinide sorption to clays (e.g. illite) under saline conditions has, however, been rarely studied. Furthermore, both illite surface and ionic strength may affect redox speciation of actinides like plutonium. In the present study, Pu sorption to illite is investigated under anaerobic conditions for 3<pHm(=-log [Formula: see text] )<10andmNaCl=1.0and3.2 molal (m). Results are compared with previous data for mNaCl=0.1m. According to redox potential measurements and based on Eu(III)-illite sorption data (taken as analogue of Pu(III)), the strong effect of mNaClon overall Pu uptake observed for pHm<6 is mainly attributed to the presence of Pu(III) and its competition with Na+for ion exchange sites. For pHm>6, overall Pu uptake is largely insensitive to mNaCldue to the prevalence of strongly adsorbed Pu(IV). By applying appropriate corrections to the activity coefficients of dissolved ions and using the 2-site protolysis non-electrostatic surface complexation and cation exchange (2 SPNE SC/CE) model, experimental data on Pu sorption to illite as a function of pH, Eh and mNaClcan be very well reproduced.
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany; Ecole Nationale Supérieure de Chimie de Rennes, UMR CNRS 6226, 11 Allée de Beaulieu, F-35708 Rennes Cedex 7, France(1).
authors.forename: Rémi
authors.initials: R
authors.lastname: Marsac
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany; Institute for Transuranium Elements, European Commission, P.O. Box 2340, D-76125 Karlsruhe, Germany(1).
authors.forename: Nidhu Lal
authors.initials: NL
authors.lastname: Banik
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany. Electronic address: johannes.luetzenkirchen@kit.edu.
authors.forename: Johannes
authors.initials: J
authors.lastname: Lützenkirchen
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany; Groupe d'Etudes Atomiques (GEA), Ecole des Applications Militaires de l'Energie Atomique (EAMEA). BCRM Cherbourg, CC19 50115 Cherbourg-Octeville Cedex, France(1).
authors.forename: Alexandre
authors.initials: A
authors.lastname: Diascorn
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Bender
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany.
authors.forename: Christian Michael
authors.initials: CM
authors.lastname: Marquardt
authors.affiliation: Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany.
authors.forename: Horst
authors.initials: H
authors.lastname: Geckeis
keywords: Clay; Illite; Ion exchange; Plutonium; Redox; Saline; Sorption; Speciation; Surface complexation model