The Sorption of Technetium and Iodine Radioisotopes by Various Minerals

Radioisotopes of technetium and iodine, elements that are present in reactor wastes, are strongly sorbed (100 ≲ K_D ≲ 2000) from aqueous solutions by several naturally occurring minerals (bournonite, chalcopyrite, pyrite, tennantite, and tetrahedrite). This is in contrast to little or no sorption (K_D < 1) in other geologic material (anhydrite, basalt, granite, and tuff). The highly sorptive behavior has been investigated using column flow and batch sorption techniques. The results indicate that oxidation reduction and mineral replacement are the mechanisms for the strong sorption of these radionuclides. Such information will be of use in the evaluation of geologic retention of nuclear wastes at future underground repository sites.