Microsoft Word - v71-22.docx

Abstract-A study concerning the photocatalytic decolourization of Congo red (CR) dye, over artificial UV irradiation is presented. Photocatalysts based on a commercial titanium dioxide (TiO 2 ) modified with transition metals (Ni, Cu and Zn) were used. The dopage method used was wet impregnation. A TiO 2 sample without salt was subjected to the same hydrothermal treatment to be used as reference. Congo red solutions to several pH conditions (natural and basic) were used to evaluate photocatalytic performance of each doped catalysts. Photodecolourization percentage was measured spectrofotrometically after 3 h of treatment to 499 nm as response variable. Kinetics investigations of photodegradation indicated that reactions obey to Langmuir-Hinshelwood model and pseudo-first order law. The rate constant studies of photocatalytic decolourization reactions for Zn-TiO 2 and Cu-TiO 2 photocatalysts indicated that in all cases the rate constant of the reaction was higher than that of TiO 2 undoped. These results show that nature of the metal modifying the TiO 2 influence on the efficiency of the photocatalyst evaluated in process. Ni does not present an additional effect compared with TiO 2 , while Zn enhances the photoactivity due to its electronic properties