Oxidative degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in subcritical and supercritical waters.
Presence of chlorinated organic compounds in water bodies has become a concern among governments, health authorities and general public. Oxidation of organic compounds in water under high temperature and pressure is considered as a promising technique, but usefulness of the technique to mineralize 2,4-dichlorophenoxyacetic acid (2,4-D) is not well understood. This article aimed to elucidate degradation characteristics of 2,4-D in both subcritical and supercritical waters by laboratory batch experiments. 2,4-D degradation, total organic carbon (TOC) removal and dechlorination increased with increasing reaction time and temperature especially in subcritical waters, while dechlorination was a major step. 2,4-dichlorophenol (2,4-DCP) and acetic acid were the main degradation intermediates both in subcritical and supercritical waters. Though 2,4-D disappeared almost completely in subcritical waters near critical region ( approximately 99%), significant amounts of TOC and organic chlorine still remained as 2,4-DCP and acetic acid. But TOC removal and dechlorination were significantly enhanced ( approximately 95 and 91% respectively) in supercritical waters. Complete mineralization of 2,4-D in subcritical waters required a considerably longer reaction period, while the mineralization was almost complete within a short reaction period in supercritical waters. This is an important information of practical significance for oxidative degradation of chlorinated pesticides similar to 2,4-D.
Hashimoto
M
M
Graduate School of Engineering, Osaka Sangyo University, 3-1-1 Nakagaito, Daito City, 574-8530 Osaka, Japan.
Taniguchi
S
S
Takanami
R
R
Giri
R R
RR
Ozaki
H
H
D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D010084:Oxidation-Reduction; D011312:Pressure; D013696:Temperature; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification
D006540:Herbicides; D014874:Water Pollutants, Chemical; D014867:Water; D015084:2,4-Dichlorophenoxyacetic Acid