fect of metal ion (commonanions with same concentration) on photoassisted bleaching of methylene blue by Nb2O5

The photo catalytic bleaching of textile azo dye Methylene blue has been carried out in the presence of semiconductor Nb2O5 and the progress of reaction was observed spectrophotometrically. The effect of various operating parameters like pH, concentration of the dye, amount of photo catalyst and nature of photo catalyst on the efficiency of the reaction has been studied. Kinetic analysis of photo degradation reveals that the degradation follows approximately pseudo first order. Attempts have been made to study the effect of addition of common cations and common anions such as Na+, K+,Ca+2, Ba+, Cl-, SO4-2 and CO3-2. It was observed that trace quantities of all the added metal ions increases the reaction rate. The increase in the photo catalytic activity may be due to introduction of new trapping sites by incorporation of transition metal ions on semiconductor surface. A tentative mechanism has been proposed.