A Study on the Degradation of Carbamazepine and Ibuprofen by TiO<sub>2</sub> & ZnO Photocatalysis upon UV/Visible-Light Irradiation

Abstract

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

Optimizing Parameters on Nanophotocatalytic Degradation of Ibuprofen Using UVC/ZnO Processes by Response Surface Methodology

“…The results of these experiments are higher than a previous study by Choina et al [13], which reached 60% abatement of ibuprofen at 5 mg/L of IBP concentration. The finding is also in agreement with another study [11] on the photocatalytic (ZnO/UV) oxidation of ibuprofen, which obtained ca. 80% degradation in 10 mg/L IBP and catalyst loading of 50 mg/L.…”

“…The desired IBP concentrations (1.5-13 mg/L) were prepared from stock by dilution in deionized water. To detect and quantify IBP, the range of concentrations in this study is higher than those typically detected in the water resources [11]. Photocatalytic experiments were carried out in a cylindrical glass reactor with workable area of 0.07×0.25 m, fitted in a cooling bath.…”

“…The following series of elementary reaction steps (Eqs. 1-8) are a simplified for reactions involving ZnO [10]: [11].…”

Degradation of Ibuprofen in Aqueous Solution with UV Light: the Effect of Reactor Volume and pH

“…As a matter of fact, the presence of trace pharmaceuticals and other xenobiotic compounds in drinking and superficial waters is a major public health concern, since little is known about the potential chronic effect on human health of the long-term ingestion of mixtures of these substances. Thus, over the past few years, both the occurrence and fate of pharmaceutical residues have attracted the interest of the scientific community (Georgaki et al 2014;Araujo et al 2014). …”

“…There is no doubt that research on the synthesis and production of pharmaceutical drugs is of primary importance for both mankind and animals (Georgaki et al 2014), but it is also worth considering that pharmaceutical residues (pharmaceutical compounds (PhACs)), excreted after application in their native form or as metabolites, contribute to the water pollution problem. Furthermore, the disposal of unused medicines from households and manufacturing facilities also contributes to the occurrence of pharmaceuticals in the environment.…”