The effect of alpha-isosaccharinic acid on the stability of and Th(IV) uptake by hardened cement paste

摘要

The effect of alpha-isosaccharinic acid (ISA) on Th(IV) uptake by hardened cement paste (HCP) has been investigated under alkaline conditions (pH 13.3). Prior to performing the uptake studies the stability of HCP was determined in the presence of ISA. It was observed that the formation of Ca-ISA complexes in solution enhances portlandite solubility. The fraction of portlandite dissolved from the HCP matrix depends on the solid to liquid (S/L) ratio of the system and the ISA concentration in solution. Th(IV) uptake by HCP was found to be reduced above an aqueous ISA concentration of about 10(-4) M. Reduction of Th(IV) uptake can be modelled taking into account the formation of a Th : ISA : Ca = 1 : 2 : 1 complex in solution. It is indicated that the formation of ternary Th(IV)-ISA complexes may be important in cement systems. The final interpretation of the data however fails due to the large uncertainties in the distribution ratios measured in the absence of ISA. [References: 29]