Degradation of C. I. Acid Orange 7 in aqueous solution by a novel electro/Fe3O4/PDS process

•A novel electro/Fe3O4/PDS process was employed to degrade Acid Orange 7 in water.•The effect of operating parameters on the degradation was investigated.•The surface properties of Fe3O4 before and after reaction was investigated by XPS.•A plausible degradation pathway of Acid Orange 7 was proposed. The decolorization of C. I. Acid Orange 7 (AO7) in aqueous solution by Fe3O4 activated peroxydisulfate (PDS) oxidation in an electrochemical reactor (EC/Fe3O4/PDS process) was performed in this study. Various parameters were investigated to optimize the process, including initial pH, current density, PDS concentration and Fe3O4 dosage. The stability of Fe3O4 particles was observed by recycle experiments. The X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface properties of Fe3O4 before and after reaction. GC–MS analysis was employed to identify the intermediate products and a plausible degradation pathway of AO7 was proposed. The change of acute toxicity during the treatment was investigated by activated sludge inhibition test. The TOC removal efficiency was 30.0% in a 90min reaction.