Photocatalytic degradation of 1,10-dichlorodecane in aqueous suspensions of TiO{sub 2}: A reaction of adsorbed chlorinated alkane with surface hydroxyl radicals

• Published in: Environmental science & technology 2000-03, Vol.34 (6)
• Main Authors: El-Morsi, T.M., Bubakowski, W.R., Abd-El-Aziz, A.S., Friesen, K.J.
• Format: Article
• Language: English
• Subjects: AQUEOUS SOLUTIONS; CHLORINATED ALIPHATIC HYDROCARBONS; ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; HYDROXYL RADICALS; MATHEMATICAL MODELS; PHOTOCHEMICAL REACTIONS; TITANIUM OXIDES; WASTE PROCESSING
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es9907360

1,10-Dichlorodecane (D{sub 2}C{sub 10}) is shown to be effectively photodegraded in aqueous suspensions of TiO{sub 2} using a photoreactor equipped with 300 nm lamps. Solutions exposed to UV light intensities of 3.6 x 10{sup {minus}5} Ein L{sup {minus}1} min{sup {minus}1}, established by ferrioxalate actinometry, showed negligible direct photolysis in the absence of TiO{sub 2} and a D{sub 2}C{sub 10} concentration approaching its solubility limit. Kinetics of photodegradation followed a Langmuir-Hinshelwood model suggesting that the reaction occurred on the surface of the photocatalyst. The presence of h{sup +}{sub vb} and OH{sm_bullet} radical scavengers, including methanol and iodide, inhibited the degradation supporting a photooxidation reaction. Electron scavengers (Ag{sup +}, Cu{sup 2+}, and Fe{sup 3+}) had small effects on the degradation rate. The lack of transformation of D{sub 2}C{sub 10} in acetonitrile as solvent indicated that the major oxidants were OH{sm_bullet} radicals. The presence of tetranitromethane, effectively eliminating the formation of free OH{sm_bullet} radicals, did not affect the degradation rates significantly. This result, combined with observed increases in photolysis rates with the degree of adsorption of D{sub 2}C{sub 10} onto the surface of the photocatalyst, confirmed that the reaction involved adsorbed 1,10-dichlorodecane and surface bound OH{sm_bullet} radicals.