Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/33557
Title: Modeling the quantum yields of herbicide 2,4-D decay in UV/H2O2 process
Authors: Chu, W 
Keywords: 2,4-D
Herbicide
Hydrogen peroxide
Kinetics
Modeling
Ultraviolet
Issue Date: 2001
Publisher: Pergamon Press
Source: Chemosphere, 2001, v. 44, no. 5, p. 935-941 How to cite?
Journal: Chemosphere 
Abstract: The photodecay of herbicide 2,4-D in a hydrogen peroxide-aided photolysis process was studied and modeled. The decay rate of 2,4-D was known to be low in the natural environment, but rate improvement was achieved in an H2O2/UV system. The 2,4-D decay quantum yields under ultraviolet (UV) light at 253.7 nm increased from 4.86 × 10-6 to 1.30 × 10-4 as the ratio of [H2O2]/[2,4-D] increased from 0.05 to 12.5. Apparently, in the presence of UV light, the decay rate of 2,4-D could be greatly improved as the concentration of hydrogen peroxide increased. However, the efficiency of 2,4-D photodecay was retarded if the concentration of H2O2 was overdosed, because the excess hydrogen peroxide consumes the hydroxyl radicals (HO·) in the solution, resulting in a much weaker oxidant HO2 ·. The decay of 2,4-D was also pH dependent. A ranking of acid (highest), base (middle) and neutral (lowest) was observed owing to the property change of reactants and the shifting of dominant mechanisms among photolysis, photohydrolysis and chemical oxidation. Two mathematical models were proposed to predict the quantum yield for various [H2O2]/[2,4-D] ratios and initial pH levels, in which very good correlation was found for the ranges of regular application.
URI: http://hdl.handle.net/10397/33557
ISSN: 0045-6535
EISSN: 1879-1298
DOI: 10.1016/S0045-6535(00)00556-7
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