Selective Uptake of Ag(I) from Aqueous Solutions Using Ionic Liquid Modified Iron Oxide Nanoparticles

Surface functionalized magnetic nanoparticles represent a potentially highly valuable tool 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 as a function of pH, exposure time, nanosorbent concentration and type of stripping agent has been investigated. Ag⁺ removal was recorded to fit the Langmuir isotherm indicating monolayer formation, with a saturation capacity of 23.69 mg/g. Moreover, optimum conditions for the selective removal of Ag⁺ in preference to Cu²⁺ and Pb²⁺, were recorded at pH 3, exposure time ranging between 0-15 min and with the highest nanosorbent concentration tested (80 mg/10ml of adsorbate solution). In addition, the most efficient stripping agent for the sorbed Ag⁺ was determined to be thiourea 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.