A contribution to the study of thorium and neptunium (IV) complexes in acidic phosphoric media

The thorium and neptunium (IV) phosphate complexes formation in acidic media has been investigated, essentially at the indicator's level with 227 Th, 234 Th, 235 Np and 239 Np. Solvent extraction, a commonly used method for determining stability constants in solutions, was used with HDEHP in toluene. In order to get a better understanding of inorganic transparent gels formation in phosphoric aqueous solutions, the effect of the thorium concentration is also studied. Specific experimental conditions have been chosen in order to avoid the formation of chelate and hydrolysis in the aqueous solution. The equilibrium constants and stability constants are calculated, and the results are compared with literature. The results show that increasing the thorium concentration does not lead to polymer forms. refs., 42 figs., 19 tabs