Effect of titanium dioxide properties and support material on photocatalytic oxidation of indoor air pollutants

Abstract

Indoor air purification through photocatalytic oxidation (PCO) has been demonstrated to be an effective technique; nevertheless, further research is needed to address some of the existing shortcomings of PCO systems. In the present study, the influence of titanium dioxide (TiO2) features and the type of support material on the performance of PCO air purifiers are investigated. TiO2 photocatalysts are prepared via hydrothermal route followed by a calcination step (300–800 °C). Calcination temperature offers a good control over the characteristics of titania, in particular crystallinity and surface area, enabling fabrication of TiO2 with the most desirable set of properties. Two support materials with distinct adsorption properties, namely nickel foam filter (NFF) and activated carbon fiber (ACF) are examined for deposition of TiO2. The developed photocatalytic filters are evaluated by the removal efficiency of methyl ethyl ketone (MEK) and the amount of generated by-products. The photocatalyst calcined at 300 °C exhibited the highest activity, which was roughly 1.6 times higher than that of commercial P25. This can be attributed to the fact that at 300 °C the best trade-off between degree of crystallinity, crystal phase/size, surface area, and surface hydroxyl groups population was reached. The steady-state MEK removal efficiency and amount of by-products were 62.2% and 180 ppb for TiO2/ACF and 36.3% and 217.5 ppb for TiO2/NFF, respectively. This synergistic effect of TiO2/ACF and the concept of in-situ regeneration of ACF are also discussed.