Abstract
We investigated the degradation of 17α-ethynylestradiol in an aqueous solution using a batch heterogeneous photocatalytic (HPC) reactor with ultraviolet (UV) light and TiO2catalyst. In order to determine appropriate operating conditions, a 23factorial experiment was conducted with initial an substrate concentration of 15 or 30 mg L-1, TiO2concentration 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% TiO2and 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% TiO2and 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 (t1/2) 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 t1/2 values of which were 44.71 and 433.12 min.
Highlights
Pharmaceuticals, persistent organic pollutants (POP) and endocrine disrupters (ED) are frequently found in effluents and surface water and on various solid matrices such as soils and sediments
When the initial substrate concentration was increased to 30 mg L-1, the degradation efficiency diminished considerably
The results presented demonstrate that the interaction between TiO2 concentration and the initial concentration of substrate exerts a strong effect on degradation efficiency, being greater at the lower values tested (i.e. 0.2% and 15 mg L-1, respectively)
Summary
Pharmaceuticals, persistent organic pollutants (POP) and endocrine disrupters (ED) are frequently found in effluents and surface water and on various solid matrices such as soils and sediments. The synthetic oestrogen 17α-ethynylestradiol (C20H24O2), which is used as an oral contraceptive and in treating the symptoms of menopause and the prevention of abortion (Ghiselli and Jardim, 2007), is one of the major contributors to ED activity in the effluent from water treatment plants (Johnson and Sumpter, 2001). Several published articles have shown that such compounds are not removed completely by the conventional processes employed in water and sewage treatment plants (Bila and Dezotti, 2007; Pereira et al, 2011). Among the various AOP strategies that have been described, heterogeneous photocatalysis (HPC), induced by radiation and performed with the help of a semiconductor, has received considerable attention because of its high efficiency in removing organic pollutants from drinking water and effluents
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