Heterogeneous Fenton process by natural pyrite for removal of a textile dye from water: Effect of parameters and intermediate identification

The ability of natural pyrite particles in the degradation of C.I. Reactive Orange 29 (RO29) solution by heterogeneous Fenton (pyrite/H₂O₂) process was studied. X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy analysis were performed to characterize the pyrite particles. The decolorization efficiency of the RO29 by pyrite/H₂O₂ process was obviously influenced by pyrite particle size, suspension pH, initial concentrations of H₂O₂ and RO29, and pyrite dosage. Decolorization efficiency of 94.4% was resulted at the initial RO29 concentration of 10 mg/L, H₂O₂ concentration of 3 mM, catalyst dosage of 3 g/L, pH of 2 and reaction time of 120 min. Decolorization efficiency through pyrite/H₂O₂ process was not decreased significantly even after five successive cycles because of the low release (0.6 mg/L) of pyrite iron in each decolorization cycle. Plausible degradation pathway of RO29 was proposed by using gas chromatography-mass spectroscopy analysis.