Photocatalytic degradation of three amantadine antiviral drugs as well as their eco-toxicity evolution

Advanced oxidation processes (AOPs) relying on in situ generated highly reactive (OH)-O-center dot are successfully applied to water purification. The absolute reaction rate constants for (OH)-O-center dot with three antiviral drugs were first reported through pulsed radiolysis experiments. Results found that (OH)-O-center dot reacted quickly with these substrates, with bimolecular reaction rate constants of 6.31 x 10(9), 5.13 x 10(9), and 7.05 x 10(9) M-1 s(-1) for 1-amantadine, 2-amantadine, and rimantadine, respectively. The photocatalytic deg-radation kinetics of substrates were followed pseudo-first-order kinetics according to Langmuir-Hinshelwood model in TiO2 suspensions, and the apparent rate constants were obtained as 0.076, 0.084, and 0.102 min(-1) for three antiviral drugs, respectively. Scavenger experiments revealed that (OH)-O-center dot was the major reactive species involved in antiviral drugs degradation. To probe the photocatalytic degradation mechanism, the fate of nitrogen elements and the change of total organic carbon were also examined, and the data showed that all three drugs could be completely mineralized into CO2, H2O, and inorganic ions (NO3- and NH4+) without generating any detectable products with enough degradation time. To further insight into the potential adverse effect of three antiviral drugs and their degradation products, the acute aquatic toxicity of degradation solutions were evaluated at three different trophic levels, and the toxicities first increased slightly and then decreased rapidly as the total organic carbon decreased. (C) 2015 Elsevier B.V. All rights reserved.