Correlation of the heterogeneous discoloration efficiency of aqueous Rhodamine-B solutions and charge separation enhancement of mixed-phase nanocrystalline titania

Heterogeneous photocatalytic removal of Rhodamine-B (RhB) dye from liquid phase was done using mixed-phase nanocrystalline TiO₂ for enhancement of charge separation and UV-visible-light-driven photocatalysis capabilities. The mixed-phase nanocrystalline TiO₂ was characterized using various analytical techniques including XRD, TEM, UV-vis DRS and PL to investigate its phase composition and structure, nanocrystalline size distribution, band gap energy, and photoluminescence properties. The photocatalytic discoloration efficiency of mixed-phase nanocrystalline titania was explored by monitoring the decomposition of RhB dye in an aqueous solution. The results showed that the as-prepared mixed-phase nanocrystalline TiO₂ was excellent for degradation of RhB molecule, and the combination of crystal phase of anatase and rutile has great effect on decomposition of RhB. The kinetic studies demonstrate that the photocatalytic oxidation reaction followed a pseudo-first-order expression due to the evidence of linear correlation between ln(c/c ₀) vs. reaction time t. Moreover, the aqueous RhB dye decomposition over the as-prepared mixed-phase nanocrystalline TiO₂ catalyst is controlled by RhB pre-adsorption.