Investigation of aquo and chloro complexes of UO2(super2+), NpO2+, Np4+, and Pu3+ by x-ray absorption fine structure spectroscopy

An experiment was conducted using edge absorption fine structure (EXAFS) spectra to identify the changes that transpire around the actinide core ions in chlorine concentration of aqueous solution. Results showed the strong influence of ion exchange medium on the formation of chloride complexes. The differences observed between the experiment and previous studies were explained by the presence of outer-sphere complexation or ion pairs. The use of other scattering techniques aside from EXAFS is suggested to identify the existence of chlorine ions at 5.0 angstrom.