(Ce-Al)-oxide pillared bentonite: A high affinity sorbent for plutonium

The ability of bentonite and montmorillonite pillared by Al-oxide and mixed (Ln-Al)-oxides (Ln = La, Ce) to remove 239plutonium solution species from water is comparatively investigated at pH 7 and pH 4. Small-angle scattering and neutron contrast variation with H2O/D2O mixtures is used to verify the ingress of water in the calcined products after hydrophilicity was introduced by an NH3-H2O vapor treatment. The size and shape of the (La/Ce)-Al oxo-hydroxy pillaring cations (2 nm spheres) is determined by small-angle x-ray scattering from the pillaring solutions. Not all of the oxide pillars improved Pu uptake compared with sodium montmorillonite. At neutral and acidic pH only (Ce-Al)-oxide pillared clays showed the ability to remove Pu over the concentration range studied (1.35 × 10−8–8 × 10−8 mol dm−3) with distribution coefficient (KD) values >104. XPS analysis of the (Ce-Al)-oxide pillared clays indicates the presence of Ce4+ as cerium dioxide. The progressive improvement in sorption performance in the order of pillar type Al2O3