In the present study the interaction of Ra(II) with calcium silicate hydrates (C-S-H) as well as with fresh and degraded hardened cement pastes (HCP) has been investigated using batch-type sorption tests. Synthetic C-S-H phases with varying CaO:SiOThe cation exchange model developed for C-S-H phases in the absence of alkalis was successfully applied to predict the sorption of Ra(II) on degraded HCP, assuming that the Ra(II) sorbs solely on the C-S-H fraction of the HCP. Model predictions and experimental data were found to agree well in view of the simplified sorption model used.
Sorption of selenium (Se) was studied by batch technique by using sedimentary rock samples andcorresponding saline groundwater from Horonobe underground research laboratory (URL)site under reducing condition. Spectroscopic analyses were performed by X-ray absorption near-edge structure (XANES) afterthe sorption experiments to identify the oxidation states of Se on the sedimentary rock. It issuggested thatthe dominant parameters affecting the Se sorption are iron-bearing minerals, especially exchangeable Fe and pyrite, and organic matters. Most of the Se sorbed on the sedimentary rock was Se(0) inthe case of natural saline groundwater, at least at relatively high Se concentration, while only part of the Se was Se(0) in caseof the synthetic groundwater, which contains no organic matters. Incorporationinto pyrite could be the sorption mechanism of Se(0).
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