Kinetics of oxidative decolorization and mineralization of Acid Orange 7 by dark and photoassisted Co2+-catalyzed peroxymonosulfate system

A kinetic model was proposed and used to interpret the experimental data for degradation of Acid Orange 7 (AO7) in aqueous solution induced by Co2+/peroxymonosulfate (Co/PMS) reagent in terms of both decolorization and mineralization. The pseudo first-order decolorization rate constants are related to [Co2+], [PMS], reciprocal of [H+] and [AO7]0. Activation energy of the AO7 decolorization process was determined to be 75.7 kJ mol−1. UV and visible light can accelerate the decolorization and mineralization process due to different mechanisms. In the combined UV/Co/PMS system, UV light can decompose PMS to generate hydroxyl (OH) and sulfate radicals (SO4-), while in the Vis/Co/PMS system, excited AO7 molecules can transfer electrons to PMS or Co3+ and thus accelerate the decomposition of PMS and catalytic cycle of Co3+/Co2+.