Green and Sustainable Catalytic Reduction of Nitroarenes Using Chitosan- and Oxidized Chitosan-Stabilized NiO Nanoparticles: A Comparative Study

Abstract

The design of sustainable nanocatalysts for the efficient reduction of toxic nitroarenes is critical for sustainable environmental remediation. In this study, nickel oxide (NiO) nanoparticles were prepared and stabilized with biopolymer-based ligands (chitosan and oxidized chitosan) to produce green nanocatalysts. The oxidized chitosan was prepared via selective oxidation of chitosan's primary hydroxyl groups to carboxylic acids, introducing additional surface functional groups that enhance metal-ligand interactions. Both nanocatalyst systems were comprehensively characterized using FTIR, XRD, SEM, TEM, UV–Vis, TGA, and BET analysis.

The catalytic efficiency of these biopolymer-stabilized NiO nanoparticles was assessed through the reduction of nitroarenes under the influence of NaBH₄. Remarkably, the oxidized chitosan-stabilized NiO nanoparticles reduced p-nitrophenol within 2 min, significantly faster than their native chitosan counterparts, which required 20 min under identical conditions, due to the enhanced electron transfer capacity and increased hydrophilicity of the oxidized chitosan matrix. Furthermore, the oxidized catalyst exhibited excellent reusability over fifteen cycles with minimal loss in activity.

This comparative investigation demonstrates the enhanced effectiveness of oxidized chitosan in biopolymer-based nanocatalysis systems and offers a sustainable approach for the remediation of nitroarene pollutants. The findings underscore the potential of oxidized chitosan functionalized nanomaterials in green chemistry and environmental applications.