title: Determination of quantum yields for the photolysis of Fe(III)-hydroxo complexes in aqueous solution using a novel kinetic method.
abstract: The determination of quantum yields for the photolysis of Fe(III)-hydroxo complexes is important for the quantitative investigation of hydroxyl radical (*OH) production, not only in a natural water body, but also in the photo-Fenton process. A novel kinetic method, using a *OH probe compound, was established for the determination of the quantum yields in this study. The method was based on measuring the pseudo-first-order rate constant of the photodecomposition of dimethylsulfoxide (DMSO) in which DMSO and its primary products scavenged the *OH at an identical rate. The preliminary experiments for the photodecomposition kinetics supported the suitability of DMSOs as a probe compound for determining quantum yields. The individual quantum yields for the photolysis of the monomeric Fe(III) complexes, in the wavelength range 240-380 nm, were determined by the photodecomposition kinetics of the hydroxyl radical (*OH) probe compound (DMSO). The determined values of the individual quantum yields were 0.046+/-0.00052 for Fe3+ (H2O)6 (hexaaquo ion) and 0.69+/-0.025 for Fe(OH)2+ (H2O)5 (hydroxypentaaquo ion) at 254 nm, and showed decreasing values with increasing wavelength, in the ranges of 240-380 nm. The quantum yields between 240 and 280 nm were newly reported in this study, and the values obtained between 280 and 380 nm were in good agreement with the literature values.
authors.affiliation: School of Chemical Engineering, College of Engineering, Seoul National University, San 56-1, Shilim-dong, Gwanak-gu, Seoul 151-742, South Korea.
authors.forename: Changha
authors.initials: C
authors.lastname: Lee
authors.forename: Jeyong
authors.initials: J
authors.lastname: Yoon
mesh_terms: D004121:Dimethyl Sulfoxide / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D010782:Photolysis; D013053:Spectrophotometry
chemical_list: D005290:Ferric Compounds; D017665:Hydroxyl Radical; D004121:Dimethyl Sulfoxide