Photocatalytic removal of spiramycin from wastewater under visible light with N-doped TiO2 photocatalysts

Heterogeneous photocatalytic processes in presence of UV light are successful to obtain complete mineralization of various pharmaceutical pollutants but no one has studied the photocatalytic removal of spiramycin under visible light irradiation. In this work, N-doped TiO2 photocatalyst active under visible light was used to evaluate the photodegradation of this antibiotic. Photocatalytic tests were carried out in a slurry photoreactor irradiated both with UV Black Light Tube and blue LEDs with spectrum emission in the visible region. Reaction products were monitored both in liquid-phase, by TOC analysis, and in gas-phase, by continuous analyzers, measuring CO and CO2 gaseous concentrations at the photoreactor outlet. The only product detected in gas-phase during UV and visible light irradiation was CO2, confirming that the photocatalytic process has been proven effective in the mineralization process of spiramycin, reaching very high values of TOC removal. A detailed mathematical modelling was performed, estimating a single value of reaction constant, able to predict the behavior of mineralization also for different initial concentrations of antibiotic. The system was effective in the removal of organic compounds present in a real pharmaceutical wastewater reaching high values of depollution in short times. It has been demonstrates the feasibility of photocatalytic visible treatment of streams containing spiramycin with N-doped TiO2, yielding in a promising method for wastewater treatment. (C) 2014 Elsevier B.V. All rights reserved.