In this work, activation of persulfate (PS) and hydrogen peroxide (H2O2) in the presence of granular activated carbon (GAC) was studied in order to investigate the degradation of Metronidazole (MTZ) antibiotic in aqueous solution. The results showed that GAC could activate PS effectively better than H2O2. Also, both adsorption and oxidation process induced MTZ removal in the GAC/PS system with remarkable synergistic effect in the combined system. After 240 min, 50% of PS was degraded and 80% of MTZ and 65% of COD were removed under the ambient conditions containing initial MTZ concentration of 100 mg L-1, PS/MTZ molar ratio of 100/1, GAC dosage of 5 g L-1 and initial pH of 3.9. Both PS degradation and MTZ removal followed pseudo first order kinetic with rate constant of 0.0006 min(-1) and 0.0023 min(-1), respectively. Scavenging study using methanol and phenol as a radical scavenger showed that most oxidation of MTZ occurred on the surface or in the boundary layer around catalyst. It was also found that MTZ removal efficiency increased when PS concentration or GAC dosage increased. However, results showed that PS loading is more effective than GAC dosage. The MTZ removal efficiency was still considerable after 4 runs reusability of GAC which implied in-situ regeneration of catalyst. It can be concluded that GAC is a favorable and promising metal-free catalyst for wastewater treatment utilization.