Photodegradation of estrone and 17β-estradiol in water

The TiO₂-assisted photodegradation of two natural female hormones, estrone (E1) and 17β-estradiol (E2), was investigated in two UV-photo-reactors, followed by solid-phase extraction and analysis by gas chromatography-mass spectrometry (GC-MS). The degradation of E1 and E2 in both reactors followed the pseudo-first-order kinetics. In reactor 1 (150 W), 97% of compounds were degraded within 4 h of irradiation. Even more rapid degradation was observed in reactor 2 (15 W) where 98% of both compounds disappeared within 1 h, due to the shorter wavelength of UV-light in reactor 2 (fixed at 253 nm) than reactor 1 (238-579 nm). The influences of different initial chemical concentrations, pH value, the presence of dissolved organic matter and hydrogen dioxide, and the catalyst concentration on the degradation rate of E1 and E2 in aqueous solutions were investigated. The results show that the extent of photo-induced degradation of E1 and E2 strongly depends on the water constituents in solution. The degradation rate was increased when pH value was increased from 2 to 7.6, beyond which the degradation rate started to decrease. The presence of humic acid enhanced the degradation of E1 and E2 in both reactors as a result of photosensitisation effect of humic acid chromophore. The degradation rate increased with an increase in H₂O₂ concentration. The degradation rate was also enhanced by increasing catalyst concentration up to 2 g/l. The findings therefore suggest that photocatalysis can be a very effective method of rapidly removing certain EDCs from water.