Catalytic reduction of 4-nitrophenol using Cu/Cu 2 O 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 (NH 2 –Fe 3 O 4 ) 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 (NaBH 4 ). 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/Cu 2 O 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 NaBH 4 as a reducing agent. The effect of the dosage of the catalyst, the initial concentrations of NaBH 4 and 4-NP were investigated. The mechanic investigation proposed Cu and Cu 2 O nanoparticles played a synergistic role on the hydrogen and electron transformation to enhance its catalytic ability. Compared with other reported catalysts, Cu/Cu 2 O 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.