Photocatalytic Degradation of 17 beta-estradiol, 17 alpha-ethinylestradiol and Bisphenol A in Different Water Matrices

Photocatalytic degradation of three endocrine disrupting chemicals (EDCs), 17 beta-estradiol, 17 alpha-ethinylestradiol and bisphenol A catalyzed by TiO2 was studied in different water matrices (Milli-Q water and tap water). The degradation profiles of each EDC followed the pseudo-first-order law. The rate constants for E2, EE2 and BPA were appreciably reduced in tap water compared to those in Milli-Q water, which can be explained by the presence of inorganic species. The major anion HCO3- in tap water restrained the degradation and 1 mmol/L HCO3- seemed to be sufficient to scavenge most hydroxyl radicals. Inhibitory effect of Ca2+ could be attributed to the aggregation of TiO2 particles. Photocatalysis of the selected EDCs was affected by the initial pH in different ways in Milli-Q water and tap water. The optimum pH was about 7 for the degradation of three selected EDCs in Milli-Q water. However, an obvious retardation was observed with the increase of pH from 3 to 12 in tap water, which was related to the existence of carbonate species. Furthermore, the coexisting humic acid greatly suppressed the photocatalytic degradation of EDCs due to competing for photons, OH-radicals and the adsorption sites. The present study was helpful to raise concern about degrading EDCs in natural waters which contains a lot of inorganic and organic compounds.