Thermodynamic Model for ThO2(am) Solubility in Isosaccharinate Solutions

Solubility of ThO2·xH2O(am) in the presence of gluconate

“…As ε(Na + , GH 4 − ) and ε(Na + , Th(OH) 2 (GH 2 ) − ) are not available, they have been estimated to be −0.07 (in analogy with ε(Na + , Hox − ) reported in [21]). A similar approach has been used pre- viously in the case of isosaccharinate complexes with thorium [14].…”

“…A number of investigations indicate that actinides may form stable complexes with polyhydroxy carboxylic acids such as gluconate [4][5][6][7][8][9][10] or isosaccharinate [7,8,[11][12][13][14], which may lead to an enhancement of their mobility. However, as far as the authors know the number of studies involving thorium and gluconate is limited [5,8], and data in absence of calcium is unpublished [6].…”

Retardation of uranium and thorium by a cementitious backfill developed for radioactive waste disposal

“…The HATCHES database provides stability constants for the complexation of Th with only two CDP ligands, isosaccharinate and acetate and the resulting model predicts no significant complexation of Th with either ligand under these experimental conditions. Mixed hydroxyl-ISA complexes, such as Th(OH)ISA 2+ , Th(OH)3(ISA)2and Th(OH)4(ISA)2 2-, have been reported (Rai et al, 2009), albeit in the absence of calcium. Some authors have suggested the formation of a calcium-thorium-ISA (Ca:ISA:Th = 1:2:1) complex in solution (Vercammen et al, , 2001Wieland et al, 2002;Gaona et al, 2008).…”

Evaluation of equilibrium constants for deprotonation and lactonisation of α-D-isosaccharinic acid

“…The ideal solubility study for this purpose must have the following attributes: (1) the solid phase used should be crystalline, rather than amorphous, 3 with rapid precipitation/dissolution kinetics, (2) the study should be conducted in the acidic region (pH < 5) with several data points per pH unit, (3) the cation of the solid phase should not: (a) make strong complexes with ISA − or if it does then the reliable complexation constant values should be available, and (b) form strong complexes with hydroxide in the low pH region, and (4) the equilibration period should be relatively long. Among the solid phases (ThO 2 (am), NpO 2 (am), PuO 2 (am), Fe(OH) 3 (am), and Ca(ISA) 2 [3,5,6,9,[20][21][22] for which solubility data in the presence of ISA are available, the only ones that meet all of the above criteria for ideal solubility study are the Ca(ISA) 2 (cr) studies by Rai et al [5,23].…”

“…1 Each of these forms produces a related cyclic molecule, a lactone (ISL) in which the isosaccharinic acid loses a water molecule. HISA is a cellulose degradation product [1][2][3][4] and is known to form strong complexes with many elements (e.g., Th, U, Np, Pu, and Am) of interest in nuclear wastes (e.g., [3,[5][6][7][8][9]). Significant quantities of HISA may be produced by degradation of cellulose in low level nuclear waste (LLW) repositories [1] so HISA-mediated mobilisation of radionuclides from LLW is of potential environmental concern.…”