Recyclable Au/SiO(2)-Shell/Fe(3)O(4)-Core Catalyst for the Reduction of Nitro Aromatic Compounds in Aqueous Solution

[Image: see text] Highly stable gold nanoparticles immobilized on the surface of amine-functionalized nanocomposite microspheres possessing a magnetite (Fe(3)O(4)) nanoparticle core and a silica (SiO(2)) shell (Au/SiO(2)-shell/Fe(3)O(4)-core) were prepared. These gold nanocomposite catalysts were tested for 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) reduction in aqueous solution in the temperature range 293–323 K and in the presence of aqueous NaBH(4) reducing agent. The magnetically recyclable gold catalyst showed high stability (∼3 months), efficient recyclability (up to 10 cycles), and high activity (∼100% conversion within 225 s, ∼700 ppm 4-NP or 2-NA). The pseudo-first-order apparent reaction rate constants (k) of 4-NP and 2-NA reduction were 7.5 × 10(–3) and 4.1 × 10(–3) s(–1), respectively, and with an apparent catalytic activity of 4.48 × 10(–8) kmol/(m(3) s).