Ultrasound irritation enhanced heterogeneous activation of peroxymonosulfate with Fe3O4 for degradation of azo dye.

Magnetic Fe3O4 nanoparticles were synthesized and used as peroxymonosulfate (PMS) activator in the presence of ultrasound (US) irritation for azo dye degradation in this study. At pH 7.0 and temperature 298K, Fe3O4 nanoparticles were able to activate PMS under ultrasound irritation to produce sulfate radicals for acid orange 7 (AO7) removal in 30min. Higher catalysts dosage, neutral pH as well as optimum values of PMS dosage and ultrasound power favored the AO7 degradation. Fe3O4 displayed excellent stability and reusability in the US/PMS system. Both of the sulfate radicals and hydroxyl radicals were produced in the reaction and sulfate radicals were the dominant according to the scavenging tests and electron paramagnetic resonance (ESR) tests. The mechanisms of ultrasound irritation enhanced PMS activation in the presence of Fe3O4 were proposed based on the results and literatures.