Fast defluorination and removal of norfloxacin by alginate/Fe@Fe3O4 core/shell structured nanoparticles

Alginate-Fe2+/Fe3+ polymer coated Fe3O4 magnetic nanoparticles (Fe3O4@ALG/Fe MNPs) with core/shell structure are prepared and used as heterogeneous Fenton nanocatalyst to degrade norfloxacin (NOF). The Fenton-like process based on Fe3O4@ALG/Fe shows much higher efficiency on NOF degradation. Compared with Fe3O4 nanoparticle-H2O2 system, NOF degradation in Fe3O4@AIG/Fe-H2O2 system can be conducted in a wide pH range (pH 3.5-6.5) and independent on temperature. With 0.98 mM H2O2 and 0.4 g L-1 Fe3O4@ALG/Fe, 100% of NOF and 90% of TOC is removed within 60 min, and the fluorine element in NOF molecule changes into F- ions within 1 min, indicating that NOF degradation in this Fenton-like reaction is performed through direct defluorination pathway. XPS analysis shows that TOC removal in reaction solution mainly results from the adsorption of NOF degradation intermediates on catalyst. Due to the paramagneticity and high saturation magnetization of Fe3O4@ALG/Fe, the used catalyst with adsorbed NOF intermediate is collected from aqueous solution by applying an external magnetic field, leading to complete removal of NOF from water samples. As being composed of inorganic materials and biopolymer, Fe3O4@ALG/Fe MNPs are robust, thermo-stable, nontoxic and environmentally friendly. These attractive features endow Fe3O4@ALG/Fe as a potent Fenton-like catalyst for fluoroquinolones degradation. (C) 2012 Elsevier B.V. All rights reserved.