XAFS STUDY OF PB(II) SORPTION AT THE ALPHA-AL2O3-WATER INTERFACE

XAFS spectra of Pb(II) adsorbed at the alpha-Al2O3-water interface were collected over a range of pH, total Pb concentration, and sorption density (Gamma) in 0.1 M NaNO3. One sample prepared in 0.1 M NaCl was also analyzed to examine the effect of the background electrolyte. As Gamma increases, sorbed Pb(II) polymerizes on the alpha-Al2O3 surface, and static disorder around Pb(II) decreases. Significant Ist and 2nd shell differences exist for samples in the two electolytes. Oxo- or hydroxo-bridged Pb(II) oligomers are believed to form at the alpha-Al2O3-water interface. The number of Pb(II) 2nd neighbors is consistent with Pb-4(OH)(4)(4+)-like complexes at the highest Gamma examined.