Magnetized biochar as a gold nanocatalyst support for p-nitrophenol reduction

Abstract

The biomass use is of considerable ecological and economical interest and here, biochar, a byproduct of biomass carbonization, is magnetized with Fe3O4 for its use as gold nanoparticle (NP) support towards catalysis of p-nitrophenol (4-NP) reduction. Biochar was synthesized from coffee straw biomass via pyrolysis, while magnetite functionalization was obtained using the precipitation method. The magnetite was identified by X-ray diffraction (XRD). The material had a specific surface area of 30 m2 g-1 and a zero point charge of 7.5. The gold NPs were deposited via reduction with NaBH4, which yielded Au and Fe3O4 NP of 4.61 and 10.9 nm, respectively. The materials were applied in the 4-NP reduction, with a rate constant kapp = (1.2 ± 0.2) × 10-2 s-1, and a synergistic effect between Au and Fe3O4 NPs was observed. Remarkably, comparison with graphene oxide to which biochar resembles showed similar behavior, and the material was reused in several catalytic cycles.