Modified palladium/chitosan/graphene nanocomposites for the reduction of nitrophenolic compounds

Abstract

Chitosan (Chit) cross-linked via glutaraldehyde to graphene oxide (GO) was prepared as the basic nanocomposite support for further modification. The Chit/GO nanocomposite was modified with carbon nanotubes (CNT) and/or magnetite (Fe₃O₄), to separate the GO sheets even further and/or to render the nanocomposite magnetic. Palladium nanoparticles (Pd NPs) was embedded into the matrix of the nanocomposite using Pd(OAc)₂ as the palladium source. SEM and TEM were used to visually investigated the sheet separation of GO, the entrapment of GO in chitosan and embedding of Pd NPs in the nanocomposite matrix. The properties of the GO nanocomposites were investigated by Attenuated Total Reflection Fourier transform infra-red spectroscopy (ATR FTIR), Thermo-Gravimetric Analysis (TGA), Inductively Coupled Plasma–Optical emission spectrometry (ICP-OES) and X-ray Photoelectron Spectroscopy (XPS). The applicability of these palladium-containing nanocomposites was investigated for the reduction of nitrophenol in the presence of NaBH₄. The reduction reactions were followed by UV-Vis and their kinetic parameter were determined. All five Pd-containing nanocomposites displayed excellent catalytic activity towards the reduction of aromatic nitroarenes. The reduction of the nitrophenol compounds over all the nanocomposites showed pseudo first order kinetics with the estimate k′_obs, between 2.0 × 10⁻³ and 2.5 × 10⁻² s⁻¹, and a possible mechanism for the reaction is proposed.

GRAPHICAL ABSTRACT

Five Pd-containing nanocomposites, have been prepared by entrapping GO in chitosan and/or incorporating CNT and/or magnetite NP additives into the nanocomposites, followed by entrapment of Pd nanoparticles. The nanocomposites exhibited excellent catalytic activity towards the reduction of nitrophenol. ATR FTIR, SEM, TEM, TGA and XPS are effective characterisation tools of these surfaces.

KEYWORDS:

• Graphene oxide (GO)
• iron oxide
• palladium nanoparticles
• chitosan
• CNT
• XPS
• reduction of nitrophenol
• nanocomposite

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This work has received support from the National Nanoscience Postgraduate Teaching and Training Platform and Sasol.