Investigation of different polymerization methods on the analytical performance of palladium(II) ion imprinted polymer materials

Palladium(II) ion imprinted polymer (IIP) materials were prepared via bulk, precipitation and suspension polymerization methods using similar compositions. In these polymerization methods, the polymerization mixture consists of a ternary complex of palladium(II) imprint ion with 8-aminoquinoline (AQ), 4-vinyl pyridine (VP, monomer), 2-hydroxyethyl methacrylate (HEMA, functional monomer), ethylene glycoldimethacrylate (EGDMA, cross-linking monomer), 2,2'-azobisisobutyronitrile (AIBN, initiator) and 2-methoxy ethanol (Porogen). Various polymerization methods were carried out by thermal means and IIP materials thus obtained were leached with 50% (v/v) HCl to obtain leached IIP particles. Control polymer (CP) particles were similarly prepared by all the three polymerization methods. The above synthesized polymer particles were characterized physically and morphologically by using FTIR, TGA, CHN, X-ray diffraction (XRD) and scanning electron microscopic (SEM) techniques. Furthermore, their capacity to rebind palladium(II) was investigated from dilute aqueous solutions and in presence of selected precious and transition elements (which are known to coexist with palladium in its mineral deposits). The rebinding studies of IIP particles obtained via bulk, precipitation and suspension methods reveal that (i) percent enrichment is quantitative with bulk and precipitation, and similar to 72% only in case of suspension; (ii) retention capacities are 28.82, 20.16 and 18.76 mg palladium(II)/g materials, respectively; (iii) selectivity for palladium(II) over other noble and transition elements lies in the order bulk similar to precipitation > emulsion. Moreover, the IIP particles obtained by all three polymerization methods exhibit imprinting effect when compared with respective CP particles. (c) 2004 Elsevier B.V. All rights reserved.