Adsorption of divalent heavy metal ions onto IDA-chelating resins: simulation of physicochemical structures and elucidation of interaction mechanisms.

The adsorption performances, under static as well as dynamic conditions, for such metal ions as Cu(II), Pb(II) and Cd(II) toward chelating resins (IRC748 and NDC702) similarly containing iminodiacetic acid group but diverse pore structures, are systematically performed and deeply exploited. The physicochemical characteristics of both IDA-chelating resins are thoroughly explored by EA, FT-IR, SEM-EDX and PSD. Langmuir isotherm and pseudo-second-order equation could satisfactorily describe the batch experimental data, based on which the equilibrium and kinetic parameters are calculated and compared. The adsorption capacities follow the order of Cu(II)>Pb(II)>Cd(II), due to the complicated impacts of metal ion electronegativity as well as resin pore textures. In the contrast of single and binary adsorption performances, more reduction of Cd(II) than Cu(II) is expectably investigated with the coexistence of competitive ion since the less affinity and hence weak competition of the former onto solid-phase. Using aqueous solution of 15 wt% HCl, nearly 100% recovery of Cu(II) and Cd(II) from IDA-resins could be strictly achieved in the column-tests. Furthermore, a schematic illustration of possible pore structure has been proposed and simulated. Meanwhile, the interaction mechanisms are thereby deduced and evidently confirmed by FT-IR as well as SEM analysis.