Neptunium, plutonium and 137Cs sorption by bentonite clays and their speciation in pore waters

SummaryThe properties of bentonite to remove radionuclides from aqueous solutions were studied as a function of pH and ionic strength. The sorption of cesium is due to ion-exchange while in the case of actinides, sorption is defined by surface complexation at neutral and slightly alkaline conditions and by both mechanisms at acidic pH. Due to the presence of Fe(II), actinides are reduced to low valence states that defines their strong retention onto bentonite and low solubilities. The solubility of both neptunium and plutonium were in the order of 2 . 10-8-4 . 10-8M with amorphous An(IV)O2 as solubility limiting phases.