Biphasic oxidation promoted by magnetic amphiphilic nanocomposites undergoing a reversible emulsion process

Abstract

Magnetic amphiphilic nanocomposites (MANCs) based on nanoalumina and carbon nanostructures were produced and applied as catalysts for biphasic reactions. These amphiphilic composites (MANCs) exhibit an excellent interaction at the interface of systems composed of immiscible liquids and can form stable emulsions between them. Being magnetic, the composites can also be used to break other stable emulsions or make the emulsions formed reversible. In this work, we report the first use of magnetic amphiphilic nanocomposites to promote biphasic reactions undergoing a magnetically reversible emulsion process. Fe and Mo catalysts were supported on the surface of nanoalumina to grow carbon nanostructures by a CVD process. To achieve the amphiphilic property, the carbon coating on the surface of the matrix is only partial. Thus, exposed iron sites can be active to catalysis. For this reason the biphasic selective oxidation of organic contaminants by hydrogen peroxide was studied. Fe species catalyze the decomposition of H₂O₂ into ˙OH very close to the substrate and intensify the biphasic reaction. The oxidized compounds are then extracted by the aqueous phase by polarity. The amphiphilic nanocomposites showed a high activity for the oxidation of model contaminants, reaching 100% of removal. The composites can be recovered by a magnetic field and reused several times with good efficiency.