Retention of Am(III) by montmorillonite: effect of sulphate

The predominant mineral, montmorillonite, in smectite-rich clays, the most promising buffer & backfill, controls their sorption characteristics towards radionuclides. The role of sulphate on Am(III) sorption by Na-montmorillonite has been investigated. The influence of pH, ionic strength & [SO 4 2 - ] on Am(III) sorption by Na-montmorillonite has been studied. The contribution of Am(III) hydroxo complexes in aqueous speciation is ~ 50% at pH 7.5 while that of Eu(III) hydroxo complexes is ~ 10%. In contrast to Eu(III), Am(III) sorption could be modeled by either ≡SOAmOH + or ≡SOAmCO 3 . Log K for Am(III) ion exchange & ≡SOAmCO 3 is less than that for similar Eu(III) species.