A Simple Method to Synthesize Three-Dimensional Network Adsorbent of Nanocellulose Dispersed Fe(OH)3 for Enhanced Adsorption of Congo Red

Abstract

The outstanding adsorption capabilities of Fe(OH)₃ nanoparticles have been widely studied for water treatment, owing to its cost-effectiveness, straightforward synthesis method, and environmental friendliness. Nevertheless, the problem of agglomeration significantly decreases its adsorption capacity, and the difficulties in separation and recycling after adsorption impede its practical use. Herein, in this work, we introduce a more cost-effective and simplified approach to fabricate porous network Fe(OH)₃/BC (bacterial cellulose) composites by adsorbing Fe³⁺ on BC nanofibers and subsequently treating them with alkali. This method enables the in situ growth of dispersed Fe(OH)₃ nanoparticles on the BC nanofibers surface, thus creating a high effective adsorbent. Moreover, anchoring Fe(OH)₃ to the surface of BC nanofibers addresses the issue of separating Fe(OH)₃ nanoparticles from the solution after adsorption. The theoretical maximum equilibrium adsorption capacity (q_m) of Fe(OH)₃/BC for congo red at pH 7, 25℃ and a shaking speed of 120 rpm reached 725.7 mg/g in 24 h, which was significantly higher than that achieved by BC or Fe(OH)₃ powder alone. In addition, Fe(OH)₃/BC exhibited excellent reusability, with removal efficiencies exceeding 92% and 78% after the 5th and 10th cycles of adsorption, respectively. This innovative approach not only simplifies fabrication processes and enables easy separation after adsorption, but also improved capacity for congo red removal.