Synthesis and characterization of magnetic iron oxide - silica nanocomposites used for adsorptive recovery of palladium (II)

Magnetic iron oxide-silica shell nanocomposites (IONP@SiO2) have been prepared in a two-step procedure. IONPs were obtained by coprecipitation of iron salts, and coated by silica in sol-gel method under sonication. Two IONP/silica ratios and two drying methods, heating in oven and supercritical CO2 drying, were used. The samples were analyzed using X-ray diffraction (XRD), infrared spectroscopy, magnetic measurements, small-angle neutron scattering (SANS), nitrogen sorption, and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX). The iron oxide silica nanocomposites obtained via supercritical drying exhibited higher values of the specific surface area and of saturation magnetization compared to the samples synthesized with the same iron oxide content but obtained after drying at 60 degrees C. Pd(II) adsorption experiments were performed on the materials prepared by supercritical drying. The maximum adsorption capacity 6.5 mg/g showed that the materials can be used as good and cheap adsorbent for palladium ions from aquatic environment.