Removal of uranium from mining industry feed simulant solutions using trapped amidoxime functionality within a mesoporous imprinted polymer material

Abstract

Ion imprinted polymer (IIP) material of mesoporous nature was prepared in two steps: (i) by forming binary/ternary complexes of uranyl imprint ion with a suitable non-vinylated uranophile, formamidoxime and/or vinylated ligand, 4-vinyl pyridine (VP) and (ii) by thermally copolymerizing them with 2-hydroxy ethyl methacrylate (HEMA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linking monomer in presence of 2,2′-azobisisobutyronitrile as initiator and 2-methoxy ethanol as porogen. The IIP material formed was subsequently leached with 50% (v/v) HCl to obtain leached materials which then rebind uranyl ions selectively from aqueous solutions. Corresponding non-imprinted polymer (NIP) materials were also prepared under the same conditions exactly as the IIP but in the absence of the uranyl ion template. Extensive characterization of IIP (both unleached and leached) and NIP materials were done using SEM, XPS, EDS, IR and BET-surface area and pore size analysis. The optimal pH for quantitative removal is 8.0–9.0 and the IIP materials offered either higher or comparable retention capacity 80.0 μmol of uranyl ion per g of polymer with respect to most of the hitherto prepared uranyl IIP materials. In addition, the imprinting effect was noticed in all the experimental variables and selectivity characteristics. The applicability of IIP material for the removal of emerging toxic pollutant uranium from uranium mining industry feed simulant solution is successfully demonstrated.