Degradation of short-chain alkyl- and alkanolamines by TiO2- and Pt/TiO2-assisted photocatalysis

The photooxidation of C2H5NH2, (C2H5)(2)NH, HOC2H4NH2, (HOC2H4)(2)NH and (H OC2H4)(3)N using TiO2 and Pt/ TiO2 as photocatalysts has been investigated. A laboratory set up was designed and a study on the influence of the conce ntration of the photocatalyst, the pH-value and the structure of the amine performed. The photocatalytic process was optimized with respect to the con centrations of the model substances during degradation. The decrease of the amine concentrations was found to be maximum at a pH of 10. The time-depen dence of the formation of cationic breakdown products, such as NH3/NH4+ and short-chain alkyl- and alkanolamines was studied by analyses with single c olumn ion chromatography. The experimental data show that the photodegradat ion follows a Langmuir-Hinshelwood kinetic. The mineralization of the model substances also was monitored by measurements of the decrease of the TOC a nd of the formation of NO2- and NO3-. The different mineralization efficien cies for the model substances studied are discussed with regard to their st ructure and adsorption behaviour on the photocatalyst, A possible breakdown mechanism involving the electrophilic attack of the hydroxyl radical is gi ven. The applicability of the TiO2-assisted photocatalytic degradation of C 2H5NH2 and (C2H5)(2)NH was tested at the pilot plant-scale with real solar radiation. The degradation rates and products obtained were similar to thos e found in the laboratory experiments. (C) 2000 Elsevier Science Ltd. All r ights reserved.