Synthesis of TiO2-based photocatalysts and their use in the degradation of the semi-precious-gemstone-coloring dye rhodamine B

In this study, new synthetic pathways for the synthesis of TiO2 were evaluated, and their application in photocatalysis was tested using rhodamine B as a probe. Thermodifferential analysis (DTA), thermogravimetric analysis (TGA), X-Ray diffraction (XRD), BET method, and scanning electron microscopy (SEM) were employed to characterize the synthesized products. The studied variables included the catalyst type (sol-gel, Pechini, electrospinning and commercial Degussa P-25), the catalyst concentration (0.5 g/L and 2 g/L), the rhodamine B concentration (5 mg/L and 10 mg/L), and the UV irradiation power (32 W and 48 W). A 200 mL reactor was used, and the parameters used to test the treatment efficiency were absorbance and ecotoxicity assays for both the untreated and treated solutions. For rhodamine B degradation, both P-25 and sol-gel TiO2 presented better photocatalytic efficiency. Ecotoxicity assays showed that the untreated solution had a highly toxic value of EC50 at 48 h (%) for Daphnia magna, whereas the solutions treated with either P-25 or sol-gel TiO2 exhibited no toxicity.