Photocatalytic Activity for NO Degradation by Construction Materials: Parametric Study and Multivariable Correlations

Various standards have been published in an effort to rationalize and unify the evaluation and quantification of photocatalytic activity. The experimental conditions stated in the published standards and test methods differ in many aspects that make it very difficult to compare different results. This paper focuses on the influence of the different parameters involved in the photocatalytic process. The photocatalytic active material consists of white mortar, surface coated by TiO2. The activity has been determined by quantifying the photocatalytic oxidation of NO. In the studied concentration interval the kinetics was estimated by a first order reaction. The influence on the activity by the relative humidity, temperature, irradiance, contaminant concentration and catalyst load has been studied. Most influent parameters are the catalyst load and light intensity until reaching plateau values at higher amount and intensity. Humidity influence the activity above 40% RH and an increased temperature lowers the activity. A global empirical correlation, including the mentioned variables, has been developed, allowing the determination of the photocatalytic activity at different environmental conditions (within the constraints of this research) and, when necessary, for comparison with reference conditions.