Decomposition of dimethyl phthalate in aqueous solution by UV–LED/TiO2 process under periodic illumination

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 2017-01, Vol.332, p.299-305
• Main Authors: Ku, Young, Shiu, Shiau-Ju, Wu, Hsuan-Chih
• Format: Article
• Language: English
• Subjects: Dimethyl phthalate; Periodic illumination; Photocatalysis; UV–LEDs
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2016.09.011

•Prolonged dark period improved DMP decomposition with higher light intensities.•The existence of more oxygen is useful for replenishing the TiO2 surface.•Photocatalytic decomposition of DMP in acidic solutions were enhanced.•Kinetic model of DMP decomposition by periodic illumination was proposed.•Roughly 50% of electric energy saving was reached for periodic illumination. The effect of controlled periodic illumination on the photonic efficiency and temporal decomposition behavior of dimethyl phthalates (DMP) in aqueous solution by UV–LED/TiO2 process was investigated in this study. For experiments conducted with the same total illumination time, the decomposition of DMP was enhanced with increasing dark period possibly ascribed to the enhancement of surface replenishment and the inhibition of electron–hole recombination. The existence of oxygen molecules might be beneficial for replenishing the TiO2 surface during the dark periods. Experiments conducted with longer illumination might not be favorable to enhance DMP decomposition, instead was more favorable for electron-hole recombination. Photocatalytic decomposition of DMP by UV–LED/TiO2 process under periodic illumination was agreeably modeled by the proposed Langmuir–Hinshelwood kinetic equation. Under the same illumination period of 5s, the calculated energy consumption per order was decreased by more than 40% for experiments conducted with the increasing dark period from 0.5 to 5.0s; thus, the electric energy consumption was substantially decreased.