Catalytic reduction of 4-nitrophenol using Cu/Cu2O nanocomposites based on magnetic maize straw

In this work, a novel copper-based nanocomposite catalyst was fabricated by using magnetic maize straw as a support for the reduction of 4-nitrophenol (4-NP). Magnetic maize straw was prepared by the amidation reaction of amine-functionalized magnetite nanoparticles (NH2–Fe3O4) with succinylated maize straw (S-MS). After magnetic succinylated maize straw (Mag-S-MS) was mixed with cupric ions aqueous solution, Cu(II) could be captured by the amino and carboxylate groups and reduced by sodium borohydride (NaBH4). The reduction product of Cu(II) was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-rays diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), which indicated binary Cu/Cu2O nanocomposites (NCs) were formed successfully on Mag-S-MS without self-aggregation and oxidation. Then, it was investigated as a catalyst for the reduction of 4-NP to 4-aminophenol (4-AP) via hydrogenation using NaBH4 as a reducing agent. The effect of the dosage of the catalyst, the initial concentrations of NaBH4 and 4-NP were investigated. The mechanic investigation proposed Cu and Cu2O nanoparticles played a synergistic role on the hydrogen and electron transformation to enhance its catalytic ability. Compared with other reported catalysts, Cu/Cu2O NCs-loaded Mag-S-MS possessed a higher catalytic efficiency for the higher rate constant value. Due to its superparamagnetic nature, it could be quickly collected from the aqueous solution under a magnetic field and it maintained relatively high catalytic activity after five cycle tests. The present study outlines a method for using agricultural waste in nanocatalytic reactions.