Electrochemical mineralization of methylene blue dye using electro-Fenton oxidation catalyzed by a novel sepiolite/pyrite nanocomposite

In the present study, heterogeneous electro-Fenton (EF) treatment using a sepiolite/pyrite (Sep/FeS2) nanocomposite was employed to degrade methylene blue (MB) dye. The morphology and structure properties of the prepared catalyst were thoroughly studied by field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and elemental mapping analysis. The EF studies were carried out in an undivided electrochemical cell equipped with a platinum (Pt) sheet as anode and graphite plate as cathode. Effects of initial pH, applied current intensity, catalyst dose and initial dye concentration on the mineralization of MB were examined, and their values were determined as 3.0, 1.0 g L−1, 50 mg L−1 and 150 mA, respectively. An almost total mineralization was acquired for a 50 mg L−1 MB solution in 75 min reaction time. The degradation mechanism using the Sep/FeS2-EF treatment was suggested with the analysis of intermediate products by liquid chromatography–mass spectrometry. Accounting for the high catalytic capability, chemical constancy and inexpensive cost, the Sep/FeS2 nanocomposite has great potential working as an EF catalyst for industrial applications.