title: Degradation of methyl orange using short-wavelength UV irradiation with oxygen microbubbles.
abstract: A novel wastewater treatment technique using 8 W low-pressure mercury lamps in the presence of uniform-sized microbubbles (diameter = 5.79 microm) was investigated for the decomposition of methyl orange as a model compound in aqueous solution. Photodegradation experiments were conducted with a BLB black light blue lamp (365 nm), a UV-C germicidal lamp (254 nm) and an ozone lamp (185 nm+254 nm) both with and without oxygen microbubbles. The results show that the oxygen microbubbles accelerated the decolorization rate of methyl orange under 185+254 nm irradiation. In contrast, the microbubbles under 365 and 254 nm irradiation were unaffected on the decolorization of methyl orange. It was found that the pseudo-zero order decolorization reaction constant in microbubble system is 2.1 times higher than that in conventional large bubble system. Total organic carbon (TOC) reduction rate of methyl orange was greatly enhanced by oxygen microbubble under 185+254 nm irradiation, however, TOC reduction rate by nitrogen microbubble was much slower than that with 185+254 nm irradiation only. Possible reaction mechanisms for the decolorization and mineralization of methyl orange both with oxygen and nitrogen mirobubbles were proposed in this study.
authors.affiliation: JST Innovation Satellite Miyazaki, 1-1 Gakuen Kibanadai Nishi, Miyazaki 889-2192, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tasaki
authors.forename: Tsubasa
authors.initials: T
authors.lastname: Wada
authors.forename: Kanji
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Shinji
authors.initials: S
authors.lastname: Kai
authors.forename: Kaoru
authors.initials: K
authors.lastname: Ohe
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Oshima
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Baba
authors.forename: Masato
authors.initials: M
authors.lastname: Kukizaki
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D003116:Color; D010100:Oxygen / Q000737:chemistry*; D010777:Photochemistry; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; C100258:methyl orange; D010100:Oxygen