Controlled bioreduction of silver ions to nanosized particles on a porous magnetic-biopolymer of carboxymethyl cellulose, Fe3O4/CMC-Ag NPs, serving as a sustainable nanocatalyst.

A magnetic-biopolymer composite of carboxymethyl cellulose (CMC), designated as Fe₃O₄@CMC, was synthesized featuring remarkable stability and an active surface with a green biosynthetic method. This composite was engineered to serve as a substrate for stabilizing silver nanoparticles (Ag NPs) with enhanced functional properties. The catalytic efficacy of the nanocatalyst, incorporating Ag NPs at concentrations of 3%, 7%, and 10%, was evaluated for the reduction of the toxic compound 4-nitrophenol to the beneficial 4-aminophenol. Among the tested configurations, the formulation containing 10% silver nanoparticles, in conjunction with Euphorbia plant extract as a bioreducing agent, exhibited the highest reduction efficiency and favorable reaction kinetics, rendering it the optimal choice. The apparent rate constant (K _app) was assessed by fine-tuning the catalyst parameters, while the reaction mechanism was further elucidated by adjusting the concentrations of NaBH₄ and 4-nitrophenol. Notably, the catalyst demonstrated good stability over five consecutive reduction cycles and could be easily retrieved from the reaction mixture using an external magnet.