Abstract
Abstract Ultraviolet (UV) irradiation is known to be effective for chemical oxidation and disinfection of water and wastewater. Recently, light emitting diode (LED) has been recognized as a cost-effective, environmentally friendly, and sustainable source of UV to replace conventional mercury lamps, so-called UV-LED. Less is known about the effectiveness of UV-LEDs, i.e., UVA, UVB, and UVC in comparison, for the decomposition of recalcitrant organic chemicals. In this study, direct photolytic decomposition and TiO 2 photocatalytic decomposition of model pharmaceuticals, including acetaminophen (ACT), diclofenac (DCF), ibuprofen (IBP), and sulfamethoxazole (SMX), was tested, and the effects of different UV-LED wavelengths on their decomposition were investigated. UV wavelength was found to be a more important parameter for the decomposition than light intensity. Shorter wavelength UV in order of UVC > UVB > UVA was more effective for the decomposition of the pharmaceuticals. Photocatalytic decomposition was much more significant than photolytic decomposition. Decomposition kinetics of the pharmaceuticals followed SMX > DCF > IBP > ACT, reflecting their molecular structures. Results on the mineralization of the pharmaceuticals also supported the observed trends for their disappearance. The investigation was resumed with microcystin-LR (MC-LR), a known lethal biological toxin often found in water resource, and the similar result to the pharmaceuticals was also observed for MC-LR. This study and the consequent results would facilitate applications of UV-LEDs for the treatment of water contaminated with recalcitrant toxic chemicals.
Published Version
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