Recyclable and Biodegradable Ag@Chitosan Nanocomposite Beads Synthesized in One-step for Catalytic Hydrogenation of 4-Nitrophenol

Abstract The study presents the in-situ synthesis of recyclable bio-nanocomposite beads based on chitosan (Cs) and silver (Ag) nanoparticles for utilization in catalytic processes. For the first time, alkaline ethanol solution was used as a physical crosslinking and reducing agent to synthesize cross-linked Ag@Cs biocomposite hydro-gel beads in one-step. The catalytic activity of the prepared beads was evaluated before and after the integration of various Ag contents through hydrogenation of toxic nitrophenol to amino-phenol, as a safer configuration. XRD, SEM, EDX, BET, UV-Vis, HRTEM, FT-IR, and TGA analyses were used to characterize the resulted samples. XRD, EDX, and optical measurements confirmed the successful immobilization of Ag into Cs beads. The grown Ag atoms are well dispersed in the Cs, with an average diameter of around 6.7 nm, according to HRTEM. Because of the synergistic effect of Ag sensitization and large surface area, the optumium Ag@Cs composite beads have high catalytic activity with a kinetic rate constant of 0.143 min − 1 , compared to 0.0001 min − 1 for pure Cs beads. Furthermore, regeneration studies were performed to ensure its catalytic stability in the removal of nitrophenol. Finally, the mechanism of Ag@Cs biocomposite hydrogel beads fabrication in a single pot was thoroughly discussed.