Decolorization of Acid Orange 7 with peroxymonosulfate oxidation catalyzed by granular activated carbon

•The GAC/PMS system can significantly induce AO7 degradation at ambient temperature.•There is a remarkable synergistic effect in the GAC/PMS combined system.•The apparent activation energy of the reaction is much low.•The adsorption of AO7 onto GAC had slight effect on PMS decomposition.•Although GAC loses its adsorption ability, it can still catalyze PMS to degrade AO7.

In this study, granular activated carbon (GAC) was used as a catalyst to activate peroxymonosulfate (PMS) to degrade azo dye Acid Orange 7 (AO7) in aqueous solution. A remarkable synergistic effect was found in the GAC/PMS combined system. The dye decolorization was much faster in the combined system than that in only GAC adsorption or PMS oxidation system. For the GAC/PMS system, the decolorization efficiency increased as the PMS concentration, the GAC dosage and the reaction temperature increased. The reaction followed a pseudo-first-order kinetic and a much lower activation energy was determined to be 25.13 kJ mol−1. The recovery performance of GAC was also studied through the GAC-reuse experiment. It was found that GAC had no obvious deactivation after four times reusing, which implied that the catalysis ability of GAC can be regenerated by the GAC/PMS combined system. Although GAC has almost lost its adsorption capacity, the GAC/PMS combined system could still significantly degrade AO7 as before. The initial reaction mechanisms were also discussed in detail.