Investigations of α-D-isosaccharinate: Fundamental Properties and Complexation

Doctoral thesis, 2005

Waste products containing cellulose will be present in the planned underground radioactive waste repositories. It will be exposed to an alkaline environment for long periods of time. Under such conditions cellulose will degrade forming mainly isosaccharinate. Sorption studies have shown that tetra- and trivalent actinides and lanthanides form strong complexes with α D isosaccharinate which increases the amount substance that goes into solution. Information relating to fundamental properties of the isosaccharinic system is scarce and needs to be attained to properly assess its long term impact on a repository. This thesis is focused on such properties of the isosaccharinic system. The acid dissociation constant of α D isosaccharinic acid and the associated enthalpy and entropy has been determined by means of potentiometric titrations. The isosaccharinic system is comprised of the three conformations α D-isosaccharinate, α-D-isosaccharinic acid and α D-isosaccharino-1,4-lactone. The equilibrium constant for the lactonization reaction has been determined by transformation rate and equilibrium studies. This information was used in complexation studies. The stability constants of thorium and americium α D-isosaccharinate have been determined using solvent extraction technique. The enthalpies and entropies associated with the thorium α D-isosaccharinate complexation have been established