Adsorption and photo catalytic degradation of crystal-violet on tungsten (VI) loaded TiO2

COUSELO N.; JOBBAGY M.; CANDAL R.J.

Chicago, IL, EE.UU

Congreso; 10th Internacional Conference on TiO2 Photocatalysis: Fundamental and Aplications; 2005

Redox Technologies

Adsorption phenomena and surface acidity have an important role in determining photocatalysts activity. In such a way, to count with surface tunable photocatalysts whose surface can be adjusted to the pollutant to be degraded, should lead to more efficient purification processes. In this work we present an approximation to the above goal based on the modification of TiO2 surface by incorporation of W(VI). TiO2 photocatalysts loaded with different amounts of W(VI) (W-TiO2) were prepared by sol-gel methods. W-TiO2 surfaces were characterized by DRX, XPS, SEM-EDX, electrophoretic mobility (zeta potential) and adsorption of crystal violet (CV). Photocatalytic activity was determined by degradation of CV at different pH’s. CV is a cationic dye, that remain positively charge between pH 3 to 8. Electrophoretic mobility measurements show that incorporation of W(VI) on TiO2 shift the iso-electric point to lower values with respect to pure TiO2. As a consequence, the surfaces, at a given pH, become more negative as the amount of W(VI) increases. The presence of W(VI) hindered crystalline growth during thermal treatment, leading to high surface area materials. Surface W(VI) concentration increases with the firing temperature. Adsorption of CV(in the dark) increases with both pH and surface tungsten concentration. Degradation rate of CV under UV illumination at a fix pH is slightly modify by W surface concentration, although CV is strongly adsorbed as tungsten loaded increases. The interaction W-TiO2–CV can be modify by tungsten surface concentration and pH. The photocatalytic activity of TiO2 is not hindered by the presence of tungsten. These results indicate that these materials are potentially tunable photocatalysts. The almost negligible effect of tungsten on degradation rate suggest that, in this particular example, adsorption is not a critical condition for photocatalysis. Presentación Oral