Abstract

Aiming to develop hydrophobic magnetic nanoparticles that are resistant to aqueous acid mediums, the synthesis, characterization, and chemical stability analysis of a magnetite/maghemite magnetic core covered with silica and functionalized with silane OTS (NANO + SILICA + OTS) were investigated. The synthesis of the magnetic core was performed by the alkaline coprecipitation method. The coat, obtained by the sol-gel method, using TEOS silane, aims to protect the magnetic core when exposed to acidic environments. The OTS silane was used as modifier for the silica surface and provides hydrophobicity to the synthesized material; as a result, such nanoparticles are capable of being dispersed in an organic liquid. The obtained results revealed that the nanoparticles have a diameter size of approximately 10 nm, a high surface area, and a superparamagnetic behavior. The coating of the nanoparticles with silica gave the iron oxide core greater protection against oxidation and attack from acid environments. And NANO + SILICA + OTS concentrations of 20 g/L and 30 g/L in the organic fluid demonstrated that iron release from the nanoparticles to the aqueous phase was lower than 0.6% of the total iron mass, even after 24-h contact in an aqueous medium with an acidity of 2 mol/L. The obtained nanoparticles are suitable for applications, even in severe acid environments.

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