Photocatalytic Degradation of Herbicide Quinmerac in Various Types of Natural Water
The efficiency of the photocatalytic degradation of the herbicide quinmerac in aqueous TiO2 suspensions was examined as a function of the type of light source, TiO2 loading, pH, temperature, electron acceptors, and hydroxyl radical (•OH) scavenger. The optimum loading of catalyst was found to be 0.25 mg mL−1 under UV light at pH 7.2, with the apparent activation energy of the reaction being 13.7 kJ mol−1. In the first stage of the reaction, the photocatalytic degradation of quinmerac (50 μM) followed approximately a pseudo-first order kinetics. The most efficient electron acceptor appeared to be H2O2 along with molecular oxygen. By studying the effect of ethanol as an •OH scavenger, it was shown that the heterogeneous catalysis takes place mainly via •OH. The results also showed that the disappearance of quinmerac led to the formation of a number of organic intermediates and ionic byproducts, whereas its complete mineralization occurred in about 120 min. The reaction intermediates (7-chloro-3-methylquinoline-5,8-dione, three isomeric phenols hydroxy-7-chloro-3-methylquinoline-8-carboxylic acids, and 7-chloro-3-(hydroxymethyl)quinoline-8-carboxylic acid) were identified and the kinetics of their appearance/disappearance was followed by LC–ESI–MS/MS. Tentative photodegradation pathways were proposed and discussed. The study also encompassed the effect of quality of natural water on the rate of removal of quinmerac.
KeywordQuinmerac Herbicide Photocatalytic degradation Titanium dioxide Photocatalytic degradation pathways Natural water
- Franzén, M., Gustafsson, K., Hallqvist, H., Niemi, L., Wallander, J., Thorin, C., & Örn, P. (2007). The impact of herbicide tolerant crops on some environmental quality objectives. <http://www2.jordbruksverket.se/webdav/files/SJV/trycksaker/Pdf_rapporter/ra07_21gb.pdf. Accessed 30 May 11.
- Navío, J. A., Macias, M., Garcia-Gómez, M., & Pradera, M. A. (2008). Functionalisation versus mineralization of some N-heterocyclic compounds upon UV-illumination in the presence of un-doped and iron-doped TiO2 photocatalysts. Applied Catalysis B: Environmental, 82(3–4), 225–232.CrossRefGoogle Scholar
- Šojić, D. V., Despotović, V. N., Abazović, N. D., Čomor, M. I., & Abramović, B. F. (2010b). Photocatalytic degradation of selected herbicides in aqueous suspensions of doped titania under visible light irradiation. Journal of Hazardous Materials, 179(1–3), 49–56.Google Scholar
- Tomlin, C. D. S. (Ed.). (2009). The pesticide manual (15th ed., pp. 1006–1007). Hampshire: Crop Protection Publications.Google Scholar
- Vione, D., Khanra, S., Cucu Man, S., Maddigapu, P. R., Das, R., Arsene, C., Olariu, R. J., Maurino, V., & Minero, M. (2009). Inhibition vs. enhancement of the nitrate-induced phototransformation of organic substrates by the •OH scavengers bicarbonate and carbonate. Water Research, 43(18), 4718–4728.CrossRefGoogle Scholar
- Zhang, W. B., An, T. C., Xiao, X. M., Fu, J. M., Sheng, G. Y., & Cui, M. C. (2003). Photochemical degradation performance of quinoline aqueous solution in presence of hydrogen peroxide. Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances & Environmental Engineering, A38(11), 2599–2611.Google Scholar