INSITU X-RAY ABSORPTION STUDY OF LEAD-ION SURFACE COMPLEXES AT THE GOETHITE WATER INTERFACE

Synchrotron-based X-ray absorption spectroscopy (XAS) provides an approach to study, in situ, the structural details of sorbed complexes. In this XAS study of Pb(II) partitioned at the goethite-water interface, it is demonstrated spectroscopically that the controlling sorption process depends on the relative and absolute concentrations of sorbate and sorbent. At low coverages the XAS results suggest that Pb forms inner-sphere surface complexes. At higher coverages, the formation of surface polymers of Pb is suggested. No evidence was obtained supporting the formation of a surface precipitate at high coverages.