Adsorption of Am(III) on red earth and natural hematite

The Am(III) adsorption isotherms on natural hematite, on a red earth and on three kinds of treated red earth samples were determined and compared. The treatment was performed to remove iron oxides, organic matter (OM) and both. The batch technique and aqueous Am(III) solutions with molarities less than 3 . 10-9 mol/l were used. A very high adsorbability of Am(III) on hematite was found, and in order to decrease the adsorption percentage, stable Eu3+ as a hold back carrier was added to the aqueous solution. All the isotherms were found to be linear. The strong effects of pH, ionic strength and fulvic acid (FA) on the Am(III) adsorption on natural hematite were demonstrated. A positive contribution of OM and an unexpectedly high negative influence of iron oxides on the Am(III) adsorption by the untreated red earth were found too. The average distribution coefficients of Am(III) adsorption on natural hematite, on red earth and on three kinds of treated red earth samples were determined, respectively, from these linear isotherms. The very high adsorbability of Am(III) on hematite and the very strong negative influence of iron oxides on the Am(III) adsorption on untreated red earth were distinctly demonstrated as well. It appears that the adsorbability of composed natural materials cannot be predicted from the adsorbabilities of each of the mineral components alone, due to possible interactions between the mineral components and the different characteristics of the composite.