Evaluating photocatalytic asphalt pavement effectiveness in real-world environments through developing models: a statistical and kinetic study

Photocatalytic asphalt pavements are evaluated in this study as a possible air-pollution reduction strategy and to comprehend their behaviour in the real-world environment. Statistical models from real-world experiments or reaction kinetics are two approaches to understand the photocatalytic reduction in real-world environments. The objective of this study was to develop a statistical model for nitrogen oxide (NO) reduction using data from a field study and to evaluate the photocatalytic reaction kinetics of NO reduction, which could be used in future theoretical air-pollution model simulations. To achieve this objective, a photocatalytic water-based spray coating was applied on an existing asphalt pavement site for the field study statistical model and on laboratory samples for the kinetic study. Based on the field data, the NO reduction was modelled using statistical regression techniques by creating a model for a non-coated pavement and photocatalytic pavement. The coefficient of determination was 0.79 and 0.67, respectively. To improve prediction, other parameters may need to be included into the model and more sampling time is required. Based on the laboratory results, the NO reduction was reaction controlled following the Langmuir–Hinshelwood (L–H) model. The adsorption equilibrium constant calculated for photocatalytic asphalt pavements was similar to those of concrete pavements while the reaction rate constant was significantly lower. While humidity has a negative correlation on both L–H constants, intensity has a positive correlation. However, interaction between these two parameters exists.