In situ synthesis of Fe3O4 nanocatalyst in chitosan-agarose hydrogel membranes for the sustainable and efficient degradation of organic compounds

Abstract

The efficient degradation of organic pollutants is critical for environmental sustainability, driving the search for eco-friendly catalytic materials. Biopolymer-based magnetic hydrogels are promising candidates, though current systems often face challenges such as poor mechanical stability, uneven nanocatalyst distribution, and complex synthesis. Here, we present a green, simple, and scalable method for fabricating chitosan–agarose dual-network hydrogels incorporating Fe3O4 nanoparticles (NPs) synthesized in situ from two iron salts. This strategy ensures uniform NPs dispersion within a mechanically robust and biocompatible matrix, enabling multifunctional hydrogels that combine catalytic efficiency, magnetic responsiveness, and reusability. The Fe3O4 content was systematically varied to tune the hydrogel’s physicochemical, mechanical, and magnetic properties. Structural characterization by X-ray diffraction and transmission electron microscopy confirmed successful in situ Fe3O4 NPs formation, with differences in size and morphology depending on the iron precursor. Rheological analysis showed increased stiffness with higher Fe3O4 content, while swelling tests revealed reduced water uptake due to pore filling. Catalytic performance was evaluated using model pollutants achieving up to 94 % degradation within 90 min under mild conditions. These nanocomposite hydrogels offer a sustainable, magnetically recoverable, and reusable platform for efficient pollutant removal, highlighting the synergistic advantages of dualbiopolymer matrices and in situ nanocatalyst formation for water remediation.

Authors acknowledge funding from MCIU/AEI /10.13039/501100011033 / FEDER, UE (PLEC2022-009279, CNS2022-136109 and PID2022-141120OB-I00) and Agència de Gestió d'Ajuts Universitaris i de Recerca de Catalunya (AGAUR) (2021 SGR 01368) for financial support. A.V. thanks AGAUR for financial support (FI-SDUR grant). J.G.-T. acknowledges the Serra Hunter program of the Generalitat de Catalunya. M.P.G. received support for the research from the Generalitat de Catalunya through the prize “ICREA Academia”. This work is also part of Maria de Maeztu Units of Excellence Programme CEX2023-001300-M funded by MCIN/AEI/10.13039/501100011033.

Peer Reviewed

Postprint (published version)