Photolytic removal and mineralisation of 2-halogenated pyridines.
The photolytic destruction and mineralisation of 2-halogenated pyridines (2-HalPYs) was studied in a range of conditions by means of ultraviolet irradiation at 254 nm. In all cases pseudo-first order kinetics satisfactorily describe the degradation process. Key decomposition products were identified and primary reaction pathways are proposed. 2-HalPYs were rapidly dehalogenated with a subsequent sharp pH drop. Complete Total Organic Carbon (TOC) removal was achieved. Their photolytic removal rate is not affected by pH or aeration. The fastest TOC removal was observed in 2-fluoropyridine (2-FPY) photolysis. 2-Hydroxypyridine (2-HPY) was identified as the primary intermediate formed by destruction of 2-chloropyridine (2-CPY), 2-bromopyridine (2-BPY) and 2-iodopyridine (2-IPY). 2-HPY is further destructed to form Dewar pyridinone. 2-FPY only marginally reacted to form 2-HPY. Instead, its major intermediate product is Dewar pyridinone. 2-IPY results in a, most likely aliphatic, photostable product, the production of which appears to increase at low pH and high 2-HPY concentration.
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
Hela
Dimitra G
DG
Papadaki
Maria
M
D002244:Carbon / Q000032:analysis; D010782:Photolysis; D011725:Pyridines / Q000032:analysis / Q000737:chemistry*; D011728:Pyridones / Q000032:analysis / Q000737:chemistry; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods*; D014873:Water Pollutants / Q000032:analysis / Q000737:chemistry*
C521930:2-fluoropyridine; C528391:2-iodopyridine; D011725:Pyridines; D011728:Pyridones; D014873:Water Pollutants; C017679:2-hydroxypyridine; D002244:Carbon; C083126:2-chloropyridine