Diazepam TiO₂ Photodegradation along with Metabolites Obtained from the Kinetic Study in Sludge

Abstract

This study aims to show the stability of diazepam, a member of the benzodiazepines and psychoactive drug, in the environment. Two experiments were carried out: biological degradation by using activated sludge and advanced oxidation processes (AOPs). AOPs process was proposed and applied. TiO₂, used as catalyst, has two important properties: high photo-catalytic activity and low cost. Photodegradation of diazepam was much faster under light irradiation in the presence of TiO₂ (half-life = 6 hours) than under Suntest irradiation (half-life = 34 hours). Considering that the photo-catalytic process started after the biological treatment on the water body containing a very little amount of contaminants, the removal of this pharmaceutical compound was quite complete and the degradation products were detected below the legal limit.