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.