DEGRADATION OF 17α-ETHINYLESTRADIOL AND ITS ESTROGENIC ACTIVITY REMOVAL BY TiO2 NANOTUBE ARRAYS IN PHOTOCATALYSIS

TiO2 nanotube arrays (TiO2 NAs) were prepared, characterized and employed as photocatalysts for the removal of 17 alpha-ethinylestradiol (EE2) and its estrogenic activity from aqueous solution for the first time. The as-synthesized TiO2 NAs were composed of well-ordered and uniform TiO2 nanotubes with pore diameter of 100 nm and length of 400 nm. EE2 was readily degraded by TiO2 NAs photocatalysis following a pseudo-first-order kinetic with an apparent rate constant of 0.0242 min(-1). More than 94% of the estrogenic activity was removed after 120-min photocatalysis since the parent compound EE2 was mainly responsible for the observed estrogenic activity. The optimum pH value for the photocatalytic degradation of EE2 is 9.0. Inorganic ions suppressed the degradation rate of EE2 in the following order: HPO42- > HCO3- > NO3-. The degradation rate was increased when the concentration of humic acid was increased from 0 to 6 mg/L, beyond which the degradation rate started to decrease. The findings, therefore, suggest that TiO2 NAs photocatalysis can be an effective method of rapidly removing certain endocrine disrupting compounds (EDCs) and estrogenic activity from water.