A Study on the Degradation of Carbamazepine and Ibuprofen by TiO2 & ZnO Photocatalysis upon UV-Visible-Light IrradiationReportar como inadecuado




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The degradation of carbamazepine CBZ and ibuprofen IBP in aqueous matrices was investigated by TiO2 and ZnO photocatalysis initiated by UV-A and visible-light irradiation. Emphasis was given on the effect of operating parameters on the degradation effectiveness, such as catalyst type and loading 50 - 500 mg-L, initial drug concentration 10, 40, 80 mg-L and wavelength of irradiation 200 - 600 nm. In an effort to understand the photocatalytic pathway for CBZ and IBP removal in terms of primary oxidants, the contribution of HO· was evaluated. With this scope, the radical-mediated process was suppressed by addition of an alcohol scavenger, isopropanol, i-PrOH, described as the best free hydroxyl radical quencher. The photodegradation rate of the pharmaceuticals was monitored by high performance liquid chromatography HPLC. According to the results, visible-light exposure, at λexc > 390 nm, takes place as a pure photocatalytic degradation reaction for both compounds. IBP was found to have overall high conversion rates, compared to CBZ. IBP oxidized fast under photocatalytic conditions, regardless the adverse effect of the increase of initial drug concentration, or low catalyst load, irradiation upon visible-light, by either titania or zinc oxide. Finally, addition of isopropanol showed a significant inhibition effect on the CBZ degradation, taken as an evidence of a solution-phase mechanism. In the case though of IBP degradation, the hole mechanism may be prevailing, suggested by the negligible effect upon addition of isopropanol indicating a direct electron transfer between holes h+ and surface-bound IBP molecules. A plausible mechanism of IBP and CBZ photocatalysis was proposed and described.

KEYWORDS

Photodegradation, Carbamazepine, Ibuprofen, Titania Photocatalysis, Zinc Oxide Photocatalysis, Oxidation Pathway

Cite this paper

Georgaki, I. , Vasilaki, E. and Katsarakis, N. 2014 A Study on the Degradation of Carbamazepine and Ibuprofen by TiO2 & ZnO Photocatalysis upon UV-Visible-Light Irradiation. American Journal of Analytical Chemistry, 5, 518-534. doi: 10.4236-ajac.2014.58060.





Autor: Irene Georgaki, Eva Vasilaki, Nikos Katsarakis

Fuente: http://www.scirp.org/



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