Degradation of 17α-ethinylestradiol in water by heterogeneous photocatalysis

Degradação de 17α-etinilestradiol em água por fotocatálise heterogênea

We investigated the degradation of 17α-ethynylestradiol in an aqueous solution using a batch heterogeneous photocatalytic (HPC) reactor with ultraviolet (UV) light and TiO₂ catalyst. In order to determine appropriate operating conditions, a 2³ factorial experiment was conducted with initial an substrate concentration of 15 or 30 mg L^-1, TiO₂ 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% TiO₂ and pH 7.0.With17α-ethynylestradiol at 15 mg L^-1, degradation efficiency was 100% after 120 min independent of TiO₂ concentration and pH. However, less than 50% of the substrate was degraded when the initial concentration was 30 mg L^-1 (0.05% TiO₂ and pH 5.0). Initial substrate concentration was a limiting factor for HPC, although the reaction was also strongly influenced by TiO₂ concentration and the interaction between initial substrate concentration and TiO₂concentration. All degradations followed first-order kinetics. With 17α-ethynylestradiol at 15 mg L^-1, the half-life time (t_1/2) 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_1/2 values of which were 44.71 and 433.12 min.

Endocrine disrupters; reaction kinetic; water treatment