Potential of Nanoparticles and Nitrates Released to Water from Photocatalytic Pavements

Abstract

Heterogeneous photocatalysis for self-cleaning and air purifying construction materials, using titanium dioxide (TiO2) nanoparticles, is a promising and fast growing technology. Much of the focus of recent research has been concentrated on understanding the photodegradation benefits such as the reduction of nitrogen oxides. Few researchers have investigated the potential adverse effects due to application of photodegradation. Potential trade-offs include the adverse environmental impact from photodegradation intermediates, photodegradation end products, or TiO2 nanoparticles released to the environment either into the atmosphere or the water. As a result, potentially harmful compounds - TiO2 nanoparticles and nitrates - released to water from photocatalytic concrete pavements were measured. The amount of nitrates eluted to water was measured after 4.5 hours of photocatalytic oxidation (PCO) of nitrogen oxide (NOx) using environmental settings, which would provide the most NOx reduced and nitrates created. After 4.5 hours of photocatalytic activity, 8.984 μmols of nitrates were released to water accounting for 49% of the theoretical amount of nitrates created. In addition, the amount of the titanium element was measured using inductive coupled plasma atomic emission spectrometry (ICP-AES). Titanium nanoparticles were not detected in any of the water samples.