Rapid sun light degradation of Rhodamine-B, Methylene blue, Methyl orange, Congo red and their binary mixtures using suprastoichiometric Bi - Molybdate

P. Suresh, A.M. Umabala, A.V. Prasada Rao

Bi₂(MoO₄)₃ with excess MoO₃ has been prepared by combustion method using Bismuth nitrate, MoO₃ and glycine. The sample as prepared showed excellent photocatalytic activity for the degradation of Rhodamine B, Methylene blue, Methyl orange and Congo red in presence of H₂O₂ under direct exposure to sun light. Complete degradation of separate 100ml aqueous solutions containing 5ppm Rhodamine B, 10ppm Methylene blue, 5ppm Methyl orange and 20ppm Congo red with 100 mg of dispersed catalyst occurred in 60, 120, 70 and 60 min respectively. Binary mixtures of aqueous solutions containing different dyes also showed complete bleaching in 60 to 150 min of exposure to sun light. Photoluminescence studies using terepthalic acid showed generation of ^.OH free radicals in the solution during irradiation. Synergitic effect is noticeable for Bi₂Mo₃O₁₂ with MoO₃ towards degradation of pure dyes as well as their mixtures.