In 2017, Cristal commissioned a third-party study of the effectiveness of titanium dioxide-based photocatalysis for air depollution in real-life situations. The study included a thorough literature search of academic work and trials carried out to date, a street canyon modelling exercise of a photocatalytic installation, and a cost benefit analysis of photocatalysis as a potential remover of NOx. Nearly 100 research papers and 12 field trials were considered.
The study concluded that the technology has significant potential to be an effective, low-cost contributor to the reduction of NOx and other airborne pollutants in urban environments. Reductions of 11-27% in NO and 4-11% in NO2 were estimated as typical.
Also highlighted in the report were a few learnings. The first is the importance of using state-of-the-art, highly active TiO2-based formulations and well-designed field applications where adequate lighting and airflow prevail. Additionally, measuring nitrate build-up on the installation surface is a more reliable test of effectiveness than traditional “before and after” measurements of ambient air quality, which are significantly influenced by uncontrollable variations in weather patterns and other external factors. And, deposition velocity is a more relevant measure of a photocatalytic surface’s effectiveness than the traditional ISO test which relies on one measurement under artificially high air pollution conditions and low gas flows.
Cristal believes this independent study shows both the strengths and weaknesses of this technology for air depollution. As evidenced by our patented formulations and ongoing development and support of CristalACTiV™ ultrafine TiO2 products, we are committed to the contribution of photocatalysis towards cleaner air.
Please see the study’s EIC Report Executive Summary for more information.
Cristal, now as part of Tronox, is continuously developing new CristalACTiV™ materials to meet existing and future environmental regulations and respond to the needs of innovative applications.