2-Hydroxypyridine photolytic degradation by 254 nm UV irradiation at different conditions.
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 degrees 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.
Stapleton
David R
DR
Chemical Engineering, IPSE, School of Process Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT, UK.
Konstantinou
Ioannis K
IK
Karakitsou
Anastasia
A
Hela
Dimitra G
DG
Papadaki
Maria
M
D002713:Chlorine / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry; D010782:Photolysis; D011728:Pyridones / Q000737:chemistry*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D016166:Free Radical Scavengers; D011728:Pyridones; D014874:Water Pollutants, Chemical; D005461:Fluorine; D002713:Chlorine; C017679:2-hydroxypyridine; D010100:Oxygen