Catalytic degradation of sulfamethoxazole and metronidazole from aqueous solution by photo-fenton process

Abstract

Residual antibiotics in environment are very reluctant to degrade under normal operating conditions. Aqueous medium of environment is polluted with undegraded or partially degraded antibiotics which is responsible for extreme water pollution. These residual antibiotics need to be treated properly as they might enter the sources of accessible safe water, even in food chain. Several conventional and advanced processes are in practice for the degradation of pollutants like antibiotics.Fenton and Fenton like processes are very popular advanced oxidation processes for the degradation of pollutants from aqueous medium. These processes are most likely to generate reactive species which are responsible for oxidation of organic pollutants such as antibiotics. It is notable that Fenton and Fenton like processes are influenced significantly by several factors such as concentration of Fenton reagent species (Fe2+ and H2O2), presence and absence of lights and pH of the solution to be degraded as well. This investigation was aimed at the degradation of sulfamethoxazole (SFX) and metronidazole (MTZ) from aqueous solution by photo-Fenton process where UV lights were used as the source of photo reaction. Four different concentrations (10, 20, 30 and 50ppm) of both the antibiotics were selected in this experiment. In order to accelerate the degradational efficiency and understand the effect of catalyst nickel ferrite nanoparticles were selected in this experiment. The catalyst was synthesized by solution combustion method and characterized with the help of x-ray diffraction, scanning electron microscope and Fourier transform infra-red spectroscopy. Effects of various reaction parameters on degradational efficiency such as pH, concentration of Fe2+ and H2O2, initial concentration of antibiotics and catalyst doses have been scrutinized in this study. The obtained results illustrated that at optimal doses (pH-4 for SFX and pH-3 for MTZ, 2 hours of reaction time and catalyst doses of 0.002 g/L, 0.004 g/L and 0.006 g/L for different concentration of antibiotics) the maximum degradation of both the antibiotics were above 90%. Furthermore, the kinetic study was also done to identify which kinetic model has been followed during the degradation process. It has been observed that degradation of SFX followed second order reaction kinetics while MTZ followed 1st order kinetic model for 20 and 30 ppm solutions and 2nd order kinetic model for 10 and 50 ppm solutions.