Photodegradation of rhodamine B in water assisted by titania films prepared through a novel procedure

Well-crystallized anatase thin films were prepared through direct oxidation of metallic titanium with 30 mass% hydrogen peroxide solution at 80 °C for 5 h, followed by soaking in distilled water at 80 °C for 3 days. The photodegradation of a dye solution, rhodamine B (RB), assisted by such deposited anatase films was studied. It was found that the well-crystallized anatase thin films induced complete degradation of RB in water with an initial concentration of less than 0.02 mM after 4–5 h of illumination under a 450 W high-pressure mercury lamp. The RB decayed directly to colorless end products of water and mineral acids. However, when the photocatalytic activity of the anatase films decreased after several repeated uses, an N-de-ethylation process producing rhodamine as an intermediate was evident during the photocatalytic degradation of RB.