We investigated the degradation of 17α-ethynylestradiol in an aqueous solution using a batch heterogeneous photocatalytic (HPC) reactor with ultraviolet (UV) light and TiO 2 catalyst. In order to determine appropriate operating conditions, a 2 3 factorial experiment was conducted with initial an substrate concentration of 15 or 30 mg L -1 , TiO 2 concentration of 0.02 or 0.05%, pH of 5.0 or 9.0 and total reaction time 240 min. Degradation profiles and kinetic parameters were determined with an initial substrate concentration of 15 or 30 mg L -1 , 0.02% TiO 2 and pH 7.0.With17α-ethynylestradiol at 15 mg L -1 , degradation efficiency was 100% after 120 min independent of TiO 2 concentration and pH. However, less than 50% of the substrate was degraded when the initial concentration was 30 mg L -1 (0.05% TiO 2 and pH 5.0). Initial substrate concentration was a limiting factor for HPC, although the reaction was also strongly influenced by TiO 2 concentration and the interaction between initial substrate concentration and TiO 2 concentration. All degradations followed first-order kinetics. With 17α-ethynylestradiol at 15 mg L -1 , the half-life time (t ½ ) was 64.16 min and the rate constant was 0.108 min -1 , while at 30 mg L -1 , substrate degradation proceeded in two stages, the t ½ values of which were 44.71 and 433.12 min.Keywords: endocrine disrupters, reaction kinetic, water treatment. Degradação de 17α-etinilestradiol em água por fotocatálise heterogênea RESUMOO objetivo desse trabalho foi investigar a degradação de 17α-etinilestradiol em solução aquosa usando um reator fotocatalítico heterogêneo em batelada com radiação ultravioleta e TiO 2 como catalisador. Com a finalidade de obter as condições ideais, um planejamento fatorial 2 3 foi realizado com concentração inicial de 15 e 30 mg L -1 , concentração de TiO 2 de 0.02 e 0.05%, variou-se o pH em 5.0 e 9.0 e tempo total de reação de 240 min. O perfil da