Sorption mechanisms of Eu3+ on CSH phases of hydrated cements

The sorption mechanisms of Eu3+ On calcium silicate hydrate (CSH) phases of hydrated cement were investigated as a tool for the prediction of the beha vior of trivalent radionuclides with aged/degraded cements in radioactive w aste repositories, Four techniques were used: site-selective and time-resol ved luminescence spectroscopy, XPS, high-resolution SEM coupled with EDX, a nd XRD, Results showed that europium is not precipitated in the solution de spite its low solubility limit. It is strongly retained on CSH, resulting i n a more than 99.8% sorption rate. Two main sorption sites were characteriz ed by luminescence spectroscopy, One site, with a long lifetime, can be int erpreted as Eu included in the framework of CSH, Another one, with a shorte r lifetime, can be interpreted as a site with a hydrated environment that i s high but is less than that of europium hydroxide. It corresponds to super ficial complexation Or precipitation. (C) 2001 Academic Press.