Indoor air NO2 depollution by photocatalysis – comparing reactor and experimental chamber results

Air quality improvement is a major concern in developed countries. In the past decade, especially in Europe, legislative measures have been taken to reduce air pollution. The present article promotes photocatalysis as an air quality improvement technique towards NO 2 pollution. Indoor air depollution by painted plasterboards treated with photocatalytic coating was investigated. First, at laboratory scale, using a bed flow reactor, depollution efficiency of the photocatalytic system was evaluated. Experimental conditions were adapted as much as possible to match indoor environment. Thus, pollution levels remained at ppb scale, temperature and relative humidity (RH) were kept constant (20 °C and 50% RH) and typical indoor lighting systems (fluorescent tubes, Light-Emitting Diode (LED) and halogen bulbs) were used for photoactivation. UV-A fluorescent tube was also used to optimise photocatalytic activity. Second, experiments were conducted at real scale, in a 10-m experimental chamber developed at our laboratory. Interior walls were covered with the photocatalytic system and the chamber was used as a reactor. Employing a specific experimental procedure, aiming at keeping pollution level constant in the chamber, photocatalytic depollution was evaluated. The same lighting systems were used for photoactivation. NO 2 abatement efficiency was evaluated through the photocatalytic oxidation potential and rate. Results show that NO 2 can be significantly removed by this technique. However, the light used for photoactivation is at utmost importance. Furthermore, the results show that at laboratory scale, photocatalytic depollution efficiency of NO 2 could be underestimated.