Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand
Two potassium oxalate doped TiO2 samples, designated as K1-TiO2 and K2-TiO2, were synthesized by the base-catalyzed sol-gel process. These samples were impregnated into rubber sheets. Two commercial TiO2 samples, anatase and Degussa P25, were used as reference materials with which the synthesized samples were to be compared. Anatase and P25 were also impregnated into rubber sheets and designated as Imp-Ana and Imp-P25, respectively. Methylene blue solution was effectively decolorized by these four impregnated sheets. Imp-K1 and Imp-K2 sheets could turn dye solutions to colorless in 3 h and remained at that point until reaching 6h. For the Imp-Ana and Imp-P25 sheets the decolorization rate was slower but increased continually until reaching their maximum at 6h (colorless). The mode of decolorization for the Impsynthesized TiO2 was mainly based on adsorption with a small contribution from the photocatalytic reaction while the reverse was observed for the Imp-commercial TiO2. The surface of the used Imp-synthsized TiO2 sheets became covered with dye after several uses but it could be cleaned by regeneration with H2O2 and UV light. After recycling the cleaned sheets could be reused many times to decolorize the dye solution.