Supported hydrophobic ionic liquid on nano-silica for adsorption of lead

Abstract

The hydrophobic character incorporated into 1-methyl-3-octylimidazolium bis(trifluoromethyl-sulfonyl)imide [OMIM +Tf 2N −] based on both the anion and cation natures was employed to develop a novel solid phase extraction medium based on physical adsorption approach. Two modified nano-silica sorbents were synthesized via direct immobilization of [OMIM +Tf 2N −] on the surface of active nano-silica [NSi-OH] and amino nano-silica [NSi-NH 2] for the formation of [NSi-OH-OMIM +Tf 2N −] and [NSi-NH 2-OMIM +Tf 2N −], respectively. Surface characterization was confirmed by TGA, FT-IR and SEM. The surface coverage values were identified in the range of 1.223–1.272 mmol g −1. Modified sorbents were extensively studied and characterized by their high similarity and affinity for lead extraction without the need for chelating intermediate. Excellent sorption capacity values (0.5–0.9 and 0.8–1.3 mmol g −1) of lead were determined in pH 1–7. Other factors such as reaction contact time, sorbent dose, initial metal ion concentration and interfering ions were studied to spot more light on the sorption capability of loaded hydrophobic ionic liquid for application in the solid phase extraction mode. These sorbents were successfully implemented for removal and preconcentration of lead from various water samples via application of a multi-stage micro-column giving rise to percentage recovery values of lead in the range of 98.0–100.0 ± 3.0–4%.