Effect of sodium persulfate as electron acceptor on antipyrine degradation by solar TiO2 or TiO2/rGO photocatalysis

In this work, a comparative study of solar photocatalytic degradation of the pharmaceutical compound antipyrine, AP, was completed. Different systems such as TiO2 alone, TiO2 modified with reduced graphene oxide (TiO2/rGO), TiO2/rGO with adddition of persulfate (TiO2/rGO/PS), and TiO2/PS were used. The catalysts characterization was carried out by X-ray diffraction, N-2 physisorption, transmission electron microscopy (TEM) and Raman spectroscopy. Initially for both TiO2 and TiO2/rGO composites, the AP adsorption kinetics was evaluated above and below their pH(ZPC). Then, the influences of different variables such as pH, TiO2 concentration, rGO load, and persulfate dosage on antipyrine solar photocatalytic degradation were determined. The solar/TiO2/PS system was found to be more efficient than the solar/TiO2/rGO/PS process. Antipyrine was completely degraded in less than 4 min, and 87% of the total organic carbon (TOC) was removed in 15 min under optimal conditions. Finally, the roles played by different reactive oxygen species, ROS, such as HO center dot, O-2(center dot-) and O-1(2), in the solar/TiO2/PS system were evaluated using appropriated scavengers.