Fe₃O₄Nanoparticles Synthesized from Waste Iron Dust for Sunlight-Boosted Photodegradation of Nitrophenols and Their Mixtures

Here, we describe a simpler-sustainable approach for fabricating photo-active magnetite nanoparticles (Fe₃O₄-NPs) using an almost inert waste material known as red-colored iron oxide dust (IOD). The synthesized heterogeneous catalyst Fe₃O₄-NPs showed photoactivity in the presence of sunlight and was used for photodegradation of a higher concentration (∼1000 mg L^-1) of noxious nitrophenols and their mixtures in an aqueous medium. Kinetic studies, including control tests, have been performed to compare the photocatalytic performance of Fe₃O₄-NPs vs IOD in sunlight and artificial bulb light. The half-life and percentage of photodegradation strongly suggest that sunlight influences the faster rate of photodegradation of nitrophenols and their mixtures. Radical trapping experiments were performed to identify the reactive active species responsible for the photodegradation, and the results support the significant involvement of hydroxyl radicals along with holes. Further, the real-life assessment of Fe₃O₄-NPs as a photocatalyst was explored by checking its photodegradation capability in industrial wastewater and soil samples via the external spiking of nitrophenols. Moreover, the results are compared with two commercially available samples of Fe₃O₄, which showed almost comparable results, and in the case of trinitrophenol (TNP) and the mixture, synthesized Fe₃O₄-NPs showed slightly better results. The quantitative studies of green chemistry metrics and DOZN software-based calculations supported the greener and more sustainable process of the present method for the synthesis of Fe₃O₄-NPs.