Iron oxide nanofibers: A new magnetic catalyst for azo dyes degradation in aqueous solution

•A simple and novel magnetic α-Fe2O3 nanofibers were successfully synthesized.•The nanofibers were used as a catalyst for the pretreatment of hardly degradable azo dye in wastewater.•The effect of variables on the decolorization efficiency was studied by chemometric design.•Under optimum condition, the decolorization efficiency of MO by α-Fe2O3 nanofibers was >99%.•The method proved to be a simple, effective with high reusability and negligible leaching of Fe ions.

In this study, a simple and novel magnetic α-Fe2O3 nanofibers were successfully synthesized by electrospinning of a solution of polyvinyl alcohol (PVA) and Fe(NO3)3·9H2O composite nanofibers followed by calcinations. These nanostructures were used as heterogeneous iron Fenton catalyst for the effective degradation and decolorization of methyl orange (MO) in aqueous solution. The initial and final concentrations of MO were determined using a UV–visible spectrophotometer. The morphologies and structures of the nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The average diameter of magnetic α-Fe2O3 nanofibers was between 50 and 90 nm. The effect of different variables on the decolorization efficiency was studied simultaneously using an experimental design. The variables of interest were as concentration of methyl orange, and H2O2, amount of catalyst, pH, temperature and time of decolorization. A Plackett–Burman design was performed for screening in order to determine the significant variables affecting the decolorization efficiency. Then, the significant factors were optimized by a Box–Behnken design (BBD) and the response surface equations were derived. Under the optimum conditions, the decolorization efficiency of methyl orange using α-Fe2O3 nanofibers was >99% in a short period time of 10 min. Finally, the developed process was successfully applied for degradation and decolorization of MO using magnetic α-Fe2O3 nanofibers as a catalyst in waste water samples.

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