Flower-like magnetite nanoparticles with unfunctionalized surface as an efficient catalyst in photo-Fenton degradation of chemical dyes

Flower-like magnetite nanoflowers (Fe₃O₄ NFs) were synthesized in this study using a new, highly scalable, modified co-precipitation method. The heterogeneous photo-Fenton process was optimized for the degradation of Rhodamine B using sodium percarbonate as an alternative source of H₂O₂. The low dosage of NPs (0.6 mg/ml) can ensure the high Rhodamine B degradation of about 93.6% at pH 4 and sodium percarbonate concentration of 8.3 mg/ml. Studies confirm the high cyclic stability of Fe₃O₄ NFs and the possibility of using optimized reaction condition in the degradation of Lissamine Green B (97.3%) and Naphthol Green B (61.8%). Moreover, it was confirmed that O₂̇⁻ and HO^∙ are the primary radicals oxidizing Rhodamine B, while the ultrafast Lissamine Green B degradation corresponds to their oxidation by O₂̇⁻. Finally, surface functionalization was confirmed as one of the most critical parameters in designing catalysts for heterogeneous photo-Fenton processes. The study confirms that in the case of surface functionalization, the degradation of dyes is slowed down (reduction of active sites on the magnetite surface by the organic molecules). Accordingly, the ultrafine, spherical-shaped magnetite nanoparticles functionalized by thrietylene glycol were characterized by above 3 times lower catalytic activity than unfunctionalized Fe₃O₄ NFs.