Δημοσίευση

The effect of basic pH and carbonate ion on the mechanism of photocatalytic destruction of cylindrospermopsin.

ΤίτλοςThe effect of basic pH and carbonate ion on the mechanism of photocatalytic destruction of cylindrospermopsin.
Publication TypeJournal Article
Year of Publication2015
AuthorsZhang, G., He X., Nadagouda M. N., O'Shea K. E., & Dionysiou D. D.
JournalWater Res
Volume73
Pagination353-61
Date Published2015 Apr 15
ISSN1879-2448
Λέξεις κλειδιάCarbonates, Chromatography, High Pressure Liquid, Hydrogen-Ion Concentration, Photolysis, Tandem Mass Spectrometry, Titanium, Uracil, Waste Disposal, Fluid, Water Pollutants, Chemical
Abstract

This study investigated the mechanistic effects of basic pH and the presence of high carbonate concentration on the TiO2 photocatalytic degradation of the cyanobacterial toxin cylindrospermopsin (CYN). High-performance liquid chromatography combined with quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS) was employed for the identification of reaction byproducts. The reaction pathways were proposed based on the identified degradation byproducts and radical chemistry. In high pH system (pH = 10.5) similar reaction byproducts as those in neutral pH system were identified. However, high pH appeared to inhibit sulfate elimination with less sulfate elimination byproducts detected. In the presence of carbonate in the photocatalytic process, hydroxyl radical reaction would be largely inhibited since carbonate ion would react with hydroxyl radical to form carbonate radical. The second order rate constant of carbonate radical with CYN was estimated to be 1.4 × 10(8) M(-1)s(-1), which is much smaller than that of hydroxyl radical. However, the more significant abundance of carbonate radical in the reaction solution strongly contributed to the transformation of CYN. Carbonate radical has higher reaction selectivity than hydroxyl radical and hence, played a different role in the photocatalytic reaction. It would promote the formation of byproduct m/z 420.12 which has not been identified in the other two studied photocatalytic systems. Besides, the presence of carbonate ion may hinder the removal of toxicity originated from uracil moiety due to the low reaction activity of carbonate radical with uracil moiety in CYN molecule. This work would further support the application of photocatalytic technologies for CYN treatment and provide fundamental information for the complete assessment of CYN removal by using TiO2 photocatalysis process.

DOI10.1016/j.watres.2015.01.011
Alternate JournalWater Res.
PubMed ID25697697

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