<i>In Situ</i> Synthesis of Ag–Fe<sub>3</sub>O<sub>4</sub> Nanoparticles Immobilized on Pure Cellulose Microspheres as Recyclable and Biodegradable Catalysts
Guozhen Wang, Fei Li, Lan Li, Jiayu Zhao, Xinxuan Ruan, Wenping Ding, Jie Cai, Ang Lu, Ying Pei
Abstract
The preparation of reusable and eco-friendly materials from renewable biomass resources such as cellulose is an inevitable choice for sustainable development. In this work, cellulose was dissolved in 7 wt % NaOH/12 wt % urea aqueous solution at −12 °C with rapid stirring. Cellulose microspheres (Cels) were fabricated by a sol–gel transition method. Subsequently, novel magnetic Ag–Fe3O4 nanoparticles (NPs) supported on cellulose microspheres were successfully constructed by an in situ one-pot synthesis. The magnetic cellulose microspheres (MCels) displayed a spherical shape with mesoporous structure and had a narrow particle size distribution (10–20 μm). Many nanopores with a pore diameter of 5–40 nm were observed in MCels. The Ag–Fe3O4 NPs were immobilized by anchoring with the hydroxyl groups on the surface of Cels. MCels were applied as a microreactor to evaluate their catalytic activities. 4-Nitrophenol (4-NP) could be reduced to 4-aminophenol (4-AP) in 5 min, catalyzed by MCels. Moreover, the magnetic microspheres exhibited a small hysteresis loop and low coercivity. Thus, MCels could be quickly gathered in water under a magnetic field in 10 s, as well as almost 9 cycle times, maintaining relatively high catalytic activity. In this work, cellulose matrix as the catalyst support could be biodegraded completely in the environment. It provided a green process for the utilization of biomass in nanocatalytic applications.