Enhanced electrodegradation of the Sunset Yellow dye in acid media by heterogeneous Photoelectro-Fenton process using Fe3O4 nanoparticles as a catalyst

Abstract

This work describes the study of sunset yellow (SY) dye degradation based on the heterogeneous electro-Fenton (EF) process, where Fe3O4 NPs were used as heterogeneous catalysts. The electrochemical system used was an undivided electrochemical cell with single compartment and a gas diffusion electrode (GDE) was used as a working electrode. The SY dye samples were analyzed by UV–vis spectrophotometry, high performance liquid chromatography (HPLC) and total organic carbon (TOC). Fe3O4 NPs were synthesized by co-precipitation method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2-physisorption analysis. For the Photoelectro-Fenton (PEF) process, the concentration decay of SY dye was 80 and 99 % in the presence of 0.1 mol L−1 Na2SO4 and 0.13 mol L−1 NaCl respectively. The results of TOC removal, showed that ∼50 % of mineralization was achieved at 90 min. For the solar Photoelectro-Fenton process (SPEF) there was high catalytic yield, i.e., 98.7 % of color removal, 100 % of concentration decay and 71 % of TOC removal at 90 min. of electrolysis. The Fe3O4 NPs stability was confirmed after eight consecutive degradation cycles, showing that there is no loss of catalytic activity at the end of the last cycle. The results obtained by XRD analysis showed that there was no structural alteration in the crystallography of the NPs after 5 h of degradation in both electrolytes. There was no dissolution of Fe2+ ions at the end of electrolysis when the SY dye was subjected to the degradation by EF, PEF and SPEF processes.