title: Effects of dissolved gas species on ultrasonic degradation of (4-chloro-2-methylphenoxy) acetic acid (MCPA) in aqueous solution.
abstract: Sonochemical degradation of MCPA ((4-chloro-2-methylphenoxy) acetic acid) in dilute aqueous solutions was studied using ultrasound with a frequency of 500 kHz. The effect of gas atmosphere on MCPA degradation was investigated in nitrogen (N(2)), air (O(2)/N(2)), oxygen (O(2)), argon (Ar) and Ar/O(2) (60/40% v/v) atmospheres. For sonochemical degradation of MCPA in N(2), air (O(2)/N(2)), O(2) and Ar atmospheres, the rate enhancement of MCPA decomposition by sonolysis was found to be more effective in an O(2)-enriched atmosphere compared to Ar atmosphere. It was considered that a higher amount of oxidants was formed in a higher O(2) partial pressure, which accelerated MCPA decomposition in a radical reaction system. On the other hand, both dechlorination and total organic carbon (TOC) removal rates were higher in Ar atmosphere, compared to those in O(2)/N(2) atmosphere. It was found that, MCPA was most effectively decomposed by sonication in Ar/O(2) (60/40% v/v) atmosphere, with higher rates of decomposition, dechlorination and TOC removal.
authors.affiliation: Research Center for Advanced Waste and Emission Management, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan. ykojima@rescwe.nagoya-u.ac.jp <ykojima@rescwe.nagoya-u.ac.jp>
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kojima
authors.forename: Takafumi
authors.initials: T
authors.lastname: Fujita
authors.forename: Erwin P
authors.initials: EP
authors.lastname: Ona
authors.forename: Hitoki
authors.initials: H
authors.lastname: Matsuda
authors.forename: Shinobu
authors.initials: S
authors.lastname: Koda
authors.forename: Naoki
authors.initials: N
authors.lastname: Tanahashi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Asakura
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000737:chemistry* / Q000528:radiation effects; D019342:Acetic Acid; D005561:Formates; D005740:Gases; D012996:Solutions; D014465:Ultrasonics; D014865:Waste Disposal, Fluid
chemical_list: D005561:Formates; D005740:Gases; D012996:Solutions; C030544:formic acid; D008456:2-Methyl-4-chlorophenoxyacetic Acid; D019342:Acetic Acid