THESIS
2016
xiv, 88 pages : illustrations ; 30 cm
Abstract
The UV/chlorine advanced oxidation process (AOP), which forms reactive species such
as hydroxyl radicals (HO•) and chlorine atoms (Cl•), is being considered as an alternative to the
UV/H
2O
2 AOP for the degradation of emerging contaminants. This study investigated the
kinetics, formation of by-products and pathways of the degradation of a recalcitrant
pharmaceutical and personal care product (PPCP)—ibuprofen (IBP)—by the UV/chlorine AOP.
The degradation of IBP followed the pseudo first-order kinetics. The first-order rate constant
was 3.3 times higher in the UV/chlorine AOP than in the UV/H
2O
2 AOP for a given chemical
molar dosage at pH 6. The first-order rate constant decreased from 3.1 × 10
-3 s
-1 to 5.5 × 10
-4 s
-1 with increasing pH from 6 to 9. Both HO• and Cl• contributed to t...[
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The UV/chlorine advanced oxidation process (AOP), which forms reactive species such
as hydroxyl radicals (HO•) and chlorine atoms (Cl•), is being considered as an alternative to the
UV/H
2O
2 AOP for the degradation of emerging contaminants. This study investigated the
kinetics, formation of by-products and pathways of the degradation of a recalcitrant
pharmaceutical and personal care product (PPCP)—ibuprofen (IBP)—by the UV/chlorine AOP.
The degradation of IBP followed the pseudo first-order kinetics. The first-order rate constant
was 3.3 times higher in the UV/chlorine AOP than in the UV/H
2O
2 AOP for a given chemical
molar dosage at pH 6. The first-order rate constant decreased from 3.1 × 10
-3 s
-1 to 5.5 × 10
-4 s
-1 with increasing pH from 6 to 9. Both HO• and Cl• contributed to the degradation, and the contribution of Cl• increased from 22% to 30% with increasing pH from 6 to 9. The effects of
water matrix in filtered drinking water on the degradation were not significant, demonstrating
the practicality of the UV/chlorine AOP for the control of some refractory PPCPs.
The degradation was initiated by HO•-induced hydroxylation and Cl•-induced chlorine
substitution, and sustained through decarboxylation, demethylation, chlorination and ring
cleavage to form more stable products. Four chlorine-containing intermediates/products were
newly identified. Significant amounts of chlorinated intermediates/byproducts were formed
from the UV/chlorine AOP. The yield of total organic chlorine (TOCl) was 31.6 μM after 90%
degradation of 50 μM IBP under the experimental conditions. The known disinfection by-products
(DBPs) comprised 17.4% of the TOCl. Subsequent chlorination followed after the
UV/chlorine AOP increased the TOCl formation to 41.06 μM, while 33.88% of which was
known DBPs. Compared to the UV/H
2O
2 AOP with subsequent chlorination, the concentrations
of TOCl and known DBPs were increased by 13.57 μM and 5.79 μM, respectively, in the
UV/chlorine AOP with subsequent chlorination.
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