TiO₂ Sensitized by Natural Dye Extracted from Cinnamon Bark for Photodegradation of Methylene Blue in Water Under LED Irradiation

This study utilizes natural-dye-sensitized photocatalysts (NDSPs) as cost-effective and ecologically safe materials for photocatalytic degradation of organic contaminants such as methylene blue (MB). A natural dye extracted from cinnamon powder has been established to sensitize TiO₂, effectively creating a visible sunlight-driven photocatalyst. The sensitization of TiO₂ by cinnamon extract was confirmed by Fourier transform infrared spectroscopy (FTIR). There was no change in the phase and morphology of TiO₂ after sensitization. The enhancement of light absorbance in the visible region of TiO₂ after being sensitized by cinnamon was confirmed by UV–visible diffused reflectance spectroscopy (DRS). The photocatalytic removal of methylene blue by cinnamon-sensitized TiO₂ (TiO₂-CI) was optimized by studying the impact of different factors (irradiation time, photocatalyst amount, pH, light power, and starting concentration of MB). Efficient removal of 87% was achieved with 100 ppm of TiO₂-CI, a pH of 10.7, and 20 ppm of MB within 20 min of visible irradiation, with an increase of 80% compared to pristine TiO₂. The photocatalytic decomposition kinetics of MB were modeled in pseudo-first order. Furthermore, the TiO₂-CI catalyst, once recovered, has the potential for regeneration with the addition of a new cinnamon extract, enabling subsequent reuse.