Portable photoreactor for on-site measurement of the activity of photocatalytic surfaces

Photocatalytic building materials, asphalts for road paving, pigments and coatings have been shown to be a promising remediation technique for air pollutants such as NOx and VOC’s. An open issue is the durability of the air cleaning characteristic in time of deployed material. Current ISO standards for photocatalytic activity testing are time consuming and cannot be used directly on-site to follow the activity of the material surface in time. The present work describes a new portable system for assessing the photo-catalytic activity of the surface of a material. The system is composed of a continuously stirred continuous flow photoreactor with a very low volume chamber (15 mL) including a 4 cm diameter opening. This opening is equipped with a gasket system that assure very good seal when the reactor lay on the surface to be tested. The gaseous phase is mixed with a UV transparent turbine. The surface is uniformly irradiated with an adjustable LED source. A gaseous stream containing a substrate (e.g. NO) is fluxed in the photoreactor. The outflow from the reactor is monitored with the proper sensor (Photoionization detector for VOC, electrochemical sensor for NOx). The portability and the low volume of the reaction chamber allow to carry out very fast measurements (few minutes) on-site, with several advantages in terms of time, costs, making very easy the durability control of deployed photocatalytic materials, also on rough surfaces. Here we report the description of the photoreactor and its characterization by using anatase TiO2 films as active materials and NO as substrate.