2-Hydroxypyridine photolytic degradation by 254 nm UV irradiation at different conditions

• Published in: Chemosphere (Oxford) 2009-11, Vol.77 (8), p.1099-1105
• Main Authors: Stapleton, David R., Konstantinou, Ioannis K., Karakitsou, Anastasia, Hela, Dimitra G., Papadaki, Maria
• Format: Article
• Language: English
• Subjects: 2-Halogenated pyridines; 2-Hydroxypyridine mineralisation; 2-Pyridinol; Air. Soil. Water. Waste. Feeding; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Biological and medical sciences; Chlorine - chemistry; Ecotoxicology, biological effects of pollution; Environment. Living conditions; Exact sciences and technology; Fluorine - chemistry; Free Radical Scavengers - chemistry; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Kinetics; Medical sciences; Models, Chemical; Oxygen - chemistry; Photolysis; Photooxidation; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Pyridones - chemistry; Reaction kinetics; Ultraviolet Rays; Water Pollutants, Chemical - chemistry
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2009.08.026

The degradation and mineralisation of (400 mL, 3.15 mM) aqueous solutions of 2-hydroxypyridine (2-HPY), a primary intermediate formed during the photolytic degradation of 2-chloropyridine (2-CPY), 2-bromopyridine (2-BPY) and 2-iodopyridine (2-IPY), was studied at 50 °C, under 254 nm UV irradiation in a range of conditions. The rate of 2-HPY disappearance was found to heavily depend on agitation, dissolved oxygen, pH and hydroxyl radical scavenger presence. pH has a pronounced effect on the phototreatment of 2-HPY, i.e. 2-HPY removal is faster at lower pH, but except for their influence on the solution pH, Cl − or F − do not appear to affect 2-HPY rate of removal or mineralisation. 2-HPY removal rate increases with dissolved oxygen, thus indicating a prominent 2-HPY photooxidation pathway. Helium purging of the solution before and during the measurement reduced 2-HPY removal rate, thus supporting the existence of a photooxidation pathway. Pure photolytic 2-HPY removal, i.e. when photooxidation is limited, fits pseudo-first order kinetics, and a kinetic model was developed for 2-HPY formation and removal during 2-CPY, 2-BPY and 2-IPY photolytic degradation under laminar flow. The addition of radical scavenger ( tert-butanol) had a detrimental effect on the photolytic degradation of 2-HPY. Complete total organic carbon removal was achieved.