g-C3N4-promoted degradation of ofloxacin antibiotic in natural waters under simulated sunlight.

This is the first report on the photodegradation of ofloxacin under simulated solar light and in actual environmental matrices in the presence of a g-C3N4 suspension. The catalyst, prepared from the polymerization of dicyandiamide (650 °C, reaction yield 60%), was characterized by means of powder X-ray diffraction (PXRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and BET surface area measurements. The experiments were carried out in a lab-scale batch reactor at concentrations in the range of micrograms/milligrams per liter. The course of the reaction was monitored by high-pressure liquid chromatography with UV-vis and fluorescence detectors. The g-C3N4-promoted photodegradation occurred at a rate 10 times faster than the direct photolysis and obeyed a first-order kinetics; in addition, the photodegradation kinetics of sonicated g-C3N4 resulted to be of the same order of that caused by P25 TiO2. Finally, the photochemical paths and the photoproducts have been identified and compared to those obtained by using P25 TiO2. From the results of this study, it can be concluded that g-C3N4 is a very attractive photocatalyst compared to P25 TiO2 in view of its ease of preparation, low cost, excellent oxidizing properties, large fraction of solar radiation absorbed, and intrinsically layered structure.