Synthesis of mesoporous TiO₂ and its role as a photocatalyst in degradation of indigo carmine dye

A modified sol–gel route without the use of acid or base was used to synthesize mesoporous TiO₂ catalyst which was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force spectroscopy, optical absorption spectroscopy and Brunauer–Emmett–Teller adsorption isotherm technique. The synthesized mesoporous TiO₂ is highly crystalline, pure and consisting of very high porosity and surface area 226.25 m² g⁻¹. The catalyst showed an excellent photocatalytic activity against the degradation of indigo carmine in the presence of visible light. It was found that 50 mL dye solution of 4 × 10⁻⁵ M concentration has been completely degraded and decolorized with optimum catalyst dose of 1.5 g/L in 180 min, acidic pH and at 25 ± 1 °C reaction temperature. The reaction kinetic was studied, and it was found that the indigo carmine dye photocatalytic degradation followed pseudo first-order reaction kinetics with rate constant, k of 0.007 min⁻¹. Degradation of dye was confirmed by chemical oxygen demand analysis and UV–Vis spectrophotometry.