Peroxymonosulfate enhanced photoelectrocatalytic degradation of 17α-ethinyl estradiol

This work aimed at the degradation of the synthetic estrogen 17α-ethinyl estradiol (EE2) via a combined photoelectrocatalysis (PEC) and peroxymonosulfate (PMS) process. Pristine and combined TiO₂/WO₃ photoanodes were fabricated and used in this work. The removal of 1 mg L⁻¹ of EE2 increased from 47.9 % to 88.8 % in 60 min by adding 10 mg L⁻¹ of PMS and an external bias of 1 V. EE2 was degraded in the presence of 0.05 M sodium sulfate as the electrolyte. The rate constant for the combined PEC-PMS process was 0.044 min⁻¹ which was higher than the rate constant of light-activated PMS process (0.0053 min⁻¹) and PEC process (0.01 min⁻¹). The rate of EE2 degradation was increased with an increase in the voltage and PMS concentration. EE2 removal was decreased and reached 62.5 % and 48.5 % when 0.05 M NaCl or 0.05 M NaClO₄ was used respectively as the electrolyte, highlighting the crucial role of electrolytes in process efficiency. Both radical and non-radical mechanisms participated in the destruction of EE2, however the role of the photogenerated carriers was dominant. Ecotoxicity using Vibrio fischeri as an indicator was decreased, although not proportionately to the parent compound EE2 in the combined Solar/TiO₂/WO₃/PMS system.