Novel Silica Sorbents Surface-Functionalized with a Salicylhydroxamic Acid-Based Ion-Imprinting Polymer for the Selective Removal of Pb(II) from Aqueous Solution

A new Pb(II)-imprinted silica sorbent IIP-SHA/SiO2 has been successfully prepared using the surface imprinting technique. The bidentate and rigid salicylhydroxamic acid was used as the chelating ligand, and a nucleophilic ring-opening reaction of glycidyl with phenolic hydroxyl group was employed as the cross-linking chemistry. The resulting ion-imprinted silica shows enhanced adsorption and more importantly remarkable selectivity toward Pb(II) and excellent reusability in both batch and dynamic adsorption experiments, making it an appealing material for Pb(II) removal from aqueous medium. The spontaneous adsorption process was found to be entropy driven and endothermic. The positive entropy change associated with the adsorption process is unusually large, indicating that the binding pockets after template ion removal are rather rigid which is believed to be responsible for the enhanced selectivity.