Open AccessXAFS study of americium sorbed onto groundwater colloids
Author(s) -
Degueldre Claude,
Reed Donald,
Kropf A. Jeremy,
Mertz Carol
Publication year - 2004
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049503024683
Subject(s) - chemistry , x ray absorption fine structure , americium , sorption , colloid , groundwater , actinide , bicarbonate , inorganic chemistry , adsorption , spectroscopy , geology , organic chemistry , physics , geotechnical engineering , quantum mechanics
The sorption of americium, as Am(III), onto groundwater colloids obtained from a marl aquifer was studied in 2 × 10 −2 M sodium bicarbonate groundwater and 2 × 10 −2 M sodium chloride bicarbonate‐free solutions. At the in situ groundwater pH of 8.6, the americium was strongly sorbed onto the colloids. XAFS analyses were performed on these sorbed Am species to establish the oxidation state and its near‐neighbour bonding. These XAFS data, obtained at 400 mg l −1 colloid concentrations and total Am concentration of 1.53 × 10 −5 M (dissolved and onto colloids), indicated that Am remains trivalent, and that surface complexes are formed with the colloids without surface precipitation. This conclusion is based on the absence of Am—Am interactions in the second or third shells. The surface complexes generated by the Am(III) sorbed onto active sites are described on the basis of the XAFS data. They include the presence of about seven water molecules around the ternary surface complexes of this trivalent actinide.