Novel core–shell structured superparamagnetic microspheres decorated with macrocyclic host molecules for specific recognition and magnetic removal of Pb(ii)

Abstract

In this work, core–shell structured superparamagnetic microspheres with highly specific recognition ability towards Pb(II), based on host–guest interactions, were developed for the first time. The four-component microspheres consist of a superparamagnetic Fe₃O₄ core, two-layer silica serving as a protection shell and functional spacer, and a macrocyclic host molecule 1,3-alternate calix[4]arene-crown-6 decorated periphery. The magnetic microspheres showed easy dispersibility, high magnetization (45.8 emu g⁻¹) and a sensitive response to an applied magnetic field. Reversible magnetic separation could be accomplished within 15 seconds. The superparamagnetic properties guaranteed convenient redispersion of the magnetic microspheres. Batch experiments revealed that the magnetic microspheres had a remarkable selectivity to Pb(II) in the presence of various interfering metals. Furthermore, the magnetic microspheres showed good stability against acid erosion for 20 days. The characterization of the structure, micro-morphology and magnetic properties of the microspheres are detailed herein. The recognition mechanism concerning the host–guest interaction and the effect of neighboring amino donors is discussed. This work offers a facile and efficient pathway to build host molecule functionalized core–shell magnetic microspheres, which have great potential for molecular recognition and separation applications.