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

Graphical abstract: - Highlights: • 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. - Abstract: 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 90 min reaction