1. Laboratoire Environnement et Minéralurgie, Nancy-University, CNRS UMR 7569, 15 avenue du Charmois, B.P. 40, 54501 Vandoeuvre-lès-Nancy Cedex, France
2. Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands