The dispersion of trace metals in contaminated soils is influenced by a variety of interfacial reactions such as precipitation/dissolution and adsorption/desorption.  Sorption processes in particular are particularly significant in dictating the mobility of trace metals due to the abundance of highly reactive substrates, such as iron-oxides, in soils. Hence, a detailed knowledge of the structure of mineral-fluid interface and binding modes of sorbates is essential for understanding the fate and transport of trace metals in the environment.In the present study, we are focused on the reaction of lead with iron-oxide surfaces.  The structure of Pb(II) at hematite (1-102) surface was determined using synchrotron based crystal truncation rod (CTR) X-ray diffraction. The results suggest that Pb forms a trigonal pyramid complex through a bidentate, corner-sharing configuration with surface (hydr)oxo groups.  The proposed surface complex structure has slightly distorted geometry with Pb-O bond lengths ranging from 2.1 � to 2.3 �.  The physical/chemical plausibility of the model was checked using both bond valence and steric analysis. The structural details presented in this study will contribute to the development of a more robust surface complexation model for describing Pb(II) dispersion in the soil environment.

Structural study of Pb(II) adsorption at hematite (1-102) surface

247th National Meeting (2014)

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