Iodine species uptake by cement and CSH studied by I K-edge X-ray absorption spectroscopy

摘要

The uptake of iodine species (I-/IO3-) by HCP (hardened cement paste) and a CSH (calcium silicate hydrate) phase under highly alkaline conditions has been investigated using X-ray absorption spectroscopy (XAS). The study was performed at the I K-edge (33.169 keV) instead of the I L-3-edge (4.557 keV) to avoid interference with Ca (K-edge = 4.038 keV) a major element in HCP and CSH phases. The XANES (X-rays absorption near-edge structure) spectra revealed no changes in the formal oxidation state of iodide (I(-I)(-)) and iodate (I(V)O-3(-)) upon uptake by HCP and CSH. The EXAFS (extended X-ray absorption fine structure) oscillations from I- treated HCP and CSH samples were found to be extremely weak, limiting interpretation of the EXAFS data. The IO3- EXAFS spectra showed that the IO3- entity consisting of three oxygen atoms with a characteristic I-O distance (similar to 1.78 Angstrom) is maintained upon uptake by HCP and CSH. XANES further indicated that CSH is not the uptake-controlling phase in HCP. [References: 29]