Selective uptake of Ag(I) from aqueous solutions using ionic liquid-modified iron oxide nanoparticles

Surface functionalized magnetic nanoparticles represent a potentially highly valuable new suite of technologies for the selective recovery of metals from the aqueous phase, due to their ability to be manipulated and then recovered using an externally applied magnetic field. Ionic liquids are ideal candidates for such surface functionalization for a range of reasons, including their enhanced selectivity, low water consumption, and high chemical stability. Herein the removal of Ag+ onto [MTESPIm](+)[Cl](-)on Fe3O4@SiO2 has been investigated as a function of pH, exposure time, nanosorbent concentration, and type of stripping agent. The Ag+ removal was recorded to fit the Langmuir isotherm indicating monolayer formation, with a saturation capacity of 23.69 mg/g. Optimum conditions for the selective removal of Ag+ in preference to Cu2+ and Pb2+ were recorded at pH 3, exposure time ranging between 0 and 15 min, and at the highest nanosorbent dose tested (80 mg nanosorbent/10 mL of adsorbate solution) Moreover, thiourea outperformed both HNO3 and HCl for the stripping of sorbed Ag+, with optimum efficacy at 0.6 M. Overall, the results indicate that [MTESPIm](+)[Cl](-) on Fe3O4@SiO2 is a highly adaptable and efficient agent for the selective recovery of Ag from the aqueous phase.