THESIS
2013
xiii, 99 p. : ill. ; 30 cm
Abstract
The kinetics of degradation of benzoic acid in the UV/chlorine process was investigated
in this research study. The UV/chlorine process has been recently considered as an efficient and
energy-saving advanced oxidation process to generate hydroxyl radicals (HO•) to degrade
emerging micropollutants. However, the photolysis of chlorine also forms the chlorine atom (Cl•),
which is a strong oxidant with standard reduction potential comparable with that of HO•. The
specific roles of HO• and Cl• on micropollutant degradation in the UV/chlorine process at
different chlorine dosages, micropullutant concentrations, pH and chloride concentrations were
thus investigated and modeled in this study. The steady-state kinetic modeling developed in this
study fitted well with the experimental dat...[
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The kinetics of degradation of benzoic acid in the UV/chlorine process was investigated
in this research study. The UV/chlorine process has been recently considered as an efficient and
energy-saving advanced oxidation process to generate hydroxyl radicals (HO•) to degrade
emerging micropollutants. However, the photolysis of chlorine also forms the chlorine atom (Cl•),
which is a strong oxidant with standard reduction potential comparable with that of HO•. The
specific roles of HO• and Cl• on micropollutant degradation in the UV/chlorine process at
different chlorine dosages, micropullutant concentrations, pH and chloride concentrations were
thus investigated and modeled in this study. The steady-state kinetic modeling developed in this
study fitted well with the experimental data and showed that the relative contributions of HO•
and Cl• to BA degradation were strongly pH-dependent and were 36% and 64% at pH 6, 17%
and 83% at pH 7.5, 2% and 98% at pH 9, respectively, in the UV/chlorine system under the
experimental conditions evaluated. The relative contributions of HO• and Cl• changed slightly
with the variations of chlorine dosages, BA concentrations and chloride concentrations. This
study firstly demonstrated quantitatively the significant contribution of Cl• in the UV/chlorine
system for BA degradation.
The formation of byproducts including chloroform (TCM), chloral hydrate (CH),
dichloropropanone (DCP), trichloropropanone (TCP), trichloroacetonitrile (TCAN),
dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) in BA degradation by the
UV/chlorine process was also studied. The byproduct formation from phenol, NOM and
fulvic acid by the UV/chlorine process was also investigated for comparison. In most cases,
statically significant increases in the byproduct formation from chlorination due to the
additional UV irradiation are commonly observed. The impacts from UV exposure were
found to be most significant in TCM formation among the five tested common disinfection
byproducts. BA was more sensitive to UV addition than was the phenol, NOM and fulvic acid.
This difference could be explained by the reactivity with chlorine. The TCM, CH, DCP, TCP
and DCAN formation in the NOM water is higher than that in the fulvic acid water, due to
their dissimilar compositions.
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