Interaction of colloids with mineral surfaces

A. Filby, M. Plaschke, H. Geckeis, Th. Fanghänel*

Institut für Nukleare Entsorgung, Forschungszentrum Karlsruhe, Postfach 3640,

D-76021 Karlsruhe, Germany

*European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe, Germany

Abstract

Adsorption of carboxylated polystyrene colloids, doped with a fluorescent dye, on Grimsel granodiorite as natural rock surface, is investigated. Adsorbed colloids are made visible by means of fluorescence microscopy and attempts are made to assign the observed fluorescence to specific mineral phases by using Scanning Electron Microscopy (SEM), energy-dispersive X-Ray Spectroscopy (EDX) and Raman-Microscopy. Increased colloid adsorption with decreasing pH has been found on both natural (rough) and polished surfaces. At pH 2 and 4 (background electrolyte 0.01 M NaCl), increased colloid sorption could be detected on Apatite, Titanite, Illite, Biotite and Feldspars (in this order). Rough surfaces generally show higher colloid adsorption than the polished ones. At pH > 6 colloid adsorption is weak and was predominantly found on natural surfaces, especially on areas with increased surface roughness.