The interaction of Sr(II) with CSH phases has been investigated to distinguish adsorption from co-precipitation processes and to assess the relevance of these processes for performance assessments. Batch-type sorption experiments were carried out to study the adsorption of Sr(II) on synthetic CSH phases at different C:S ratios. Co-precipitation experiments were conducted by precipitating CSH phases in the presence of Sr(II) at two different precipitation rates.
Distribution ratios (Rd) of Sr(II) obtained from the sorption and co-precipitation studies were found to be similar in value. The results indicate that co-precipitation processes do not enhance Sr(II) uptake by CSH compared to adsorption. In both the co-precipitation and adsorption experiments the same sorption sites are accessible to Sr(II). The precipitation rate of the CSH phases has no significant influence on the Rd values.