A comparative study on adsorption and photocatalytic degradation of VOCs by Mn-Oxides modified TiO2 micro-particles

The results presented in this work concern the study of the adsorption and the photocatalytic degradation of VOCs by TiO2-based catalysts modified with Mn. Ethanol and toluene were selected because they are the major indoor air pollutants, whereby photocatalytic properties of TiO2 are insignificant because of the need of UV light. Mn absorbs the visible light. Its deposition on TiO2 can be performed by different methods, leading to specific catalyst features that strongly affect the final photocatalytic performance. Thus, we synthesized four Mn-TiO2 catalysts by impregnation at different pH (3-12). The pollutants exhibit a stronger affinity for the catalysts synthesized at lower pH, i.e. they are adsorbed more strongly. Furthermore, the Mn- TiO2 synthesized at pH 3 mineralizes the pollutants efficiently (20 % ethanol degraded in 20 h). Results showed that varying the pH, the catalyst behavior change, and in turn, the performance depended on the affinity of the organic molecule for the catalyst. Overall, we aim at increasing the knowledge about visible- light active materials, correlating their chemical properties to their photocatalytic performance.