Chlorine/UV treatment of anatoxin-a by activation of the secondary amine functional group

Studies of the combined application of chlorine and UVC radiation (Cl/UV) have generally focused on target compound degradation by the combined effects of direct photolysis and reactions with radical intermediates. However, prechlorination also has the potential to impart structural changes on molec...

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Bibliographic Details
Published in:Environmental science water research & technology 2020-05, Vol.6 (5), p.1412-142
Main Authors: Chen, Moshan, Blatchley, Ernest R
Format: Article
Language:English
Subjects:
Activation
Amines
Chlorination
Chlorine
Chlorine compounds
Decomposition reactions
Degradation
Functional groups
Intermediates
Oxidation
Photodecomposition
Photodegradation
Photolysis
Radiation
Ultraviolet radiation
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Summary:Studies of the combined application of chlorine and UVC radiation (Cl/UV) have generally focused on target compound degradation by the combined effects of direct photolysis and reactions with radical intermediates. However, prechlorination also has the potential to impart structural changes on molecules that increase their sensitivity to direct photolysis. Specifically, the prechlorination of amines leads to formation of their N -chlorinated derivatives, which is important because the N-Cl bond is photolabile. The Cl/UV process was examined for degradation of the secondary amines anatoxin-a (ANTX-a) and dimethylamine. ANTX-a and dimethylamine were both shown to undergo rapid N -chlorination. The first-order rate constant for photodecomposition of N -chlorodimethylamine at 254 nm was estimated to be 1.13 ± 0.05 × 10 −3 cm 2 mJ −1 , while dimethylamine does not absorb UV 254 radiation. The photodegradation of Cl-ANTX-a was also observed to be faster than direct photolysis of ANTX-a. For comparison, a first-order rate constant for photodegradation of Cl-ANTX-a of 1.86 ± 0.05 × 10 −3 cm 2 mJ −1 at 254 nm was estimated for N -chlorinated anatoxin-a, as compared 1.19 ± 0.02 × 10 −3 cm 2 mJ −1 for anatoxin-a. The observed increase in first-order rate of photodegradation illustrated activation of anatoxin-a toward photolysis by prechlorination. A UV treatment process with prechlorination promotes the direct UV photodegradation of anatoxin-a by forming an N-Cl bond on the amine group.
ISSN:2053-1400
2053-1419
DOI:10.1039/c9ew01112a