Comparison of photodegradative rate of rhodamine B assisted by two kinds of TI02 films

Rhodamine B (RB) was used as a molecular probe to make a comparison of the photocatalytic properties between a P-25 coated film and a dip-coated anatase Ti02 film. It was found that RB on the two illuminated TiO2 surfaces underwent very different changes. The reduction of RB concentration on a P-25 film showed pseudo first-order kinetics during all the reaction time. In contrast, the concentration of the RB aqueous solution with an anatase Ti02 film did not show exponential decay through overall illumination time, but the kinetics of RB (or rhodamine) disappearance was apparently first order with respect to time before and after blue shift of the maximum absorbance (corresponding to N-de-ethylation) ended separately.