<i>Ilex paraguariensis</i> Extract-Coated Magnetite Nanoparticles: A Sustainable Nano-adsorbent and Antioxidant

Abstract

Single-crystal 15 nm size magnetite nanoparticles were synthesized and coated with Yerba Mate (Ilex paraguariensis) extract to evaluate their use as versatile antioxidant magnetic nanoadsorbents. The obtained particles, Mnp@YM, were found to be composed of a crystalline magnetite core surrounded by a shell composed of Fe3O4, FeO, and Fe2O3 oxides. YM extract resulted an effective protective coating for Mnp incorporating surface carboxylates, phenols, and organic N groups which improve the particles stability in aqueous suspensions. Mnp@YM antioxidant capacity (1.8 µM Trolox equivalent per 0.1 mg YM coating contained in 1 mgL−1 particle suspension) is of the order reported for polyphenols. SO4 ⋅− scavenging rate constant (1.5×104 g−1 L s−1 ) is within the diffusion controlled regime for 15 nm spherical nanoparticles with homogeneously distributed reactive sites. Mnp@YM reversibly adsorbs MB with maximum adsorption of 50 mg g−1 . As a consequence of these capacities, Mnp@YM resulted effective in preventing MB oxidation by peroxodisulfate.