Comparison of different methods to asses the photocatalytic performance of building materials

MARÍA DE LOS MILAGROS BALLARI; JOS H.J.H. BROUWERS

Bordeaux

Simposio; European Symposium on Photocatalysis, (JEP 2011); 2011

European Photocatalysis Federation

The employment of photocatalytic building materials containing titanium dioxide (TiO2) is becoming an alternative solution to improve the air quality in highly polluted areas. By using this technology it is possible to degrade a wide range of air contaminants mainly emitted by automobiles, like nitric oxide (NO) and nitrogen dioxide (NO2). Currently, there are many methodologies available to assess the photocatalytic efficiency of semiconducting materials at lab scale, some of them already in the form of international and national standards. The most common target pollutant employed in these tests is the NO (ISO 22197-1), but also others use a mixture of NO and NO2 to perform the assessment (UNI 11247, XP B44-011). On the other hand, the operating conditions of the experimental setup, like irradiance, relative humidity and pollution level, the photoreactor size (and consequently the sample area) and its operation mode (batch or continuous, stirred or flow reactors) can vary significantly. Therefore, the comparison of their results is not directly possible. Even more, a very large difference between the reported pollutant conversions can be observed. In the present paper, the photocatalytic degradation of NO using roof waterproofing membranes as a matrix for TiO2 provided by the company ICOPAL is studied applying two different experimental procedures. One of them is in concordance with the standard ISO 22197-1 employing a continuous flow reactor that can reach the steady state quickly. The other experimental device uses comparable conditions of irradiance and relative humidity and also operates continuously, but the reactor volume is larger and it is well stirred. A very good correlation between the experimental data and the theoretical calculations is obtained. This allows predicting in advance of the photocatalytic performance of a certain material according to one test having the experimental result of another.