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The Decomposition Kinetics of Monocrotophos in Aqueous Solutions by the Hydrogen Peroxide–Ozone Process
Author(s) -
Ku Young,
Wang Wen
Publication year - 1999
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143099x121652
Subject(s) - chemistry , hydrogen peroxide , aqueous solution , decomposition , ozone , radical , mineralization (soil science) , inorganic chemistry , monocrotophos , chemical process of decomposition , nuclear chemistry , medicinal chemistry , organic chemistry , nitrogen , pesticide , agronomy , biology
Decomposition of monocrotophos in an aqueous solution by the hydrogen peroxide–ozone (H 2 O 2 –O 3 ) process was studied under various solution pHs and H 2 O 2 –O 3 ) molar ratios. Experimental results indicated that monocrotophos could be almost completely (>95%) decomposed by the H 2 O 2 –O 3 ) process within 20 minutes. Formation of carbon dioxide was observed, followed by the formation of nitrate and phosphate. A simplified kinetic model, consisting of three two‐step consecutive reactions based on elemental mass balances, was found to accurately describe the temporal behaviors of reacting species during the decomposition of monocrotophos in aqueous solution by the H 2 O 2 –O 3 ) process. In most experiments, acidic conditions favored the disappearance of monocrotophos, possibly because of breakage of the carbon–carbon double bond to form various organic intermediates, but mineralization of organic intermediates by free radical hydroxyl (OH·) attack was more favored in alkaline conditions. The decomposition of monocrotophos by the H 2 O 2 –O 3 ) process was found to be significantly affected by the mode of H 2 O 2 addition. For the batch mode of H 2 O 2 addition, increased H 2 O 2 dose reduced the decomposition rate, possibly because large amounts of H 2 O 2 added initially served as a scavenger for OH· free radicals. For the continuous mode of H 2 O 2 addition, increased H 2 O 2 dose accelerated reaction rates of monocrotophos until an optimum H 2 O 2 –O 3 ) molar ratio was reached, which was found to vary for different solution pHs.