Novel application of FeIn2S4 as an efficient photo-Fenton catalyst for degradation of Ponceau 4R in aqueous solution

The chalcogenide composite FeIn2S4 was prepared by hydrothermal route and, for the first time, investigated as a heterogeneous catalyst in the photo-Fenton treatment for Ponceau 4R dye (C20H11N2Na3O10S3) under visible irradiation. The composite was characterized by X-ray diffraction (DRX), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectrometry (EDS) and elemental mapping, band gap energy and X-ray photoelectron spectroscopy (XPS). The optimal experimental conditions were investigated and determined to be pH 3.0, 0.5 g L−1 of catalyst and 2.5 mmol L−1 of H2O2. A decolorization efficiency of 93.3% was achieved in 60 min of reaction and a TOC removal of 92.3% was reached in 180 min. The stability and recycle capacity of FeIn2S4 indicated that the catalyst can be used more than four times without considerable loss of efficiency. Free radicals investigation revealed that •OH and O2•− radicals were the major oxygen reactive species involved on Ponceau 4R degradation. The lower-mass intermediates from Ponceau 4R degradation were identified, and a mechanism for the photo-Fenton treatment was suggested. Therefore, the composite showed a performance that makes it a promising catalyst for removing emerging contaminants in water.