Application of response surface methodology to the decolorization by the electrochemical process using FePMo12O40 catalyst

Abstract In order to optimize the experimental conditions, the decolorization of Acid Red 3R by electrochemical oxidation process with catalyst FePMo 12 -APS-MS4A as packing was performed using response surface methodology (RSM). The microstructure and morphology of FePMo 12 -APS-MS4A were characterized with Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). Four control factors were throughly analyzed by means of RSM based on Box–Behnken design (BBD). Taking the decolorization efficiency as response value, a second order polynomial model was established. The model and analysis strongly indicated that the cell voltage and airflow caused positive, and the initial pH and inter-electrode distance caused negative effect on the decolorization efficiency. The interaction between cell voltage and initial pH, initial pH and airflow were also revealed. Under the optimal conditions, the color, COD and TOC removal efficiency reached 67.3%, 58.4% and 47.9% after 60 min. Liquid chromatography–mass spectrometry (LC–MS) analysis revealed that the dye molecule underwent a series of reduction and oxidation steps, including azo bond fracture, desulfonation and denitrogenation. The possible mechanisms involving in this reaction process were proposed.