Degradation of antipyrine (AP) in water by three UV-based photolysis processes (i.e., direct UV, UV/H2O2, UV/persulfate (UV/PS)) was studied. For all the oxidation processes, the AP decomposition exhibited a pseudo-first-order kinetics pattern. Generally, UV/H2O2 and UV/PS significantly improved the degradation rate relevant to UV treatment alone. The pseudo-first-order degradation rate constants (k(obs)) were, to different degrees, affected by initial AP concentration, oxidant dose, pH, UV irradiation intensity, and co-existing chemicals such as humic acid, chloride, bicarbonate, carbonate and nitrate. The three oxidation processes followed the order in terms of treatment costs: UV/PS > UV > UV/H2O2 if the energy and chemical costs are considered. Finally, the AP degradation pathways in the UV/H2O2 and UV/PS processes are proposed. Results demonstrated that UV/H2O2 and UV/PS are potential alternatives to control water pollution caused by emerging contaminants such as AP. (C) 2013 Elsevier B.V. All rights reserved.