Photocatalytic degradation of Azure and Sudan dyes using nano TiO2.

The present study investigates the dependence of photocatalytic rate on molecular structure of the substrate that is degraded. The photocatalytic degradation of Azure (A and B) and Sudan (III and IV) dyes, having similar structure, but different functional groups, were investigated with two catalysts. The photocatalytic activity of solution combustion synthesized TiO(2) (CS TiO(2)) was compared with that of Degussa P-25 for degrading these dyes. The effect of solvents and mixed-solvent system on photodegradation of Sudan III was investigated. The photodegradation rate was found to be higher in solvents with higher polarity. The effect of pH and the presence of metal ions in the form of chloride and nitrate salt, on degradation rate of Azure A was also investigated. The metal ions significantly reduced the photocatalysis rates. A detailed Langmuir-Hinshelwood kinetic model has been developed to explain the effect of metal ions on degradation rate of the substrate. This model elucidates the contribution of holes and electrons towards degradation of the dye.

Substitution effect on the photocatalytic degradation by the series AxBi26-xMo10O68+0.5y (A = Ba, y = 0; A = Bi, La, y = 2): a kinetic study.

The compounds Ba2Bi24Mo10O68 and La2Bi24Mo10O69 were synthesized by the ceramic route and characterized by single crystal and powder X-ray diffraction, respectively. The structure of these phases is isostructural with that of Bi26Mo10O69. Along the b axis columns of [Bi12O14] units are separated by MoO4 tetrahedra and noncolumnar A (A = Ba, La) atoms. UV-visible spectra of Bi26Mo10O69, Ba2Bi24Mo10O68, and La2Bi24Mo10O69 suggest that band gap decreases on substitution of La and Ba for Bi at the noncolumnar site. The photocatalytic degradation of water pollutants such as phenol and substituted phenols was studied. All the catalysts show specificity toward nitro substituent at the para position in the aromatic ring.