Photocatalytic NOx removal efficiency and surface reflectance of carbonated mortars

Abstract

Photocatalytic concrete containing titanium dioxide (TiO2) nanoparticles can convert airborne nitrogen oxides (NOx) into nitrate byproducts when exposed to light in the UV-A spectrum, which can reduce the impact to the environment and humans. In this study, the photocatalytic degradation of NOx by mortars containing anatase TiO2 was analyzed through photoreactor testing. Mortar mixtures were prepared with white and gray cements and varying TiO2 and fly ash contents to quantify the effects of carbonation and surface reflectance on each mix design’s NOx removal potential. Carbonation of the mortar specimens significantly reduced photocatalytic NOx removal efficiency, but this could be offset by the replacement of cement with fly ash. Specimens containing photocatalytic white cement were highly reflective in the UV-A spectrum and demonstrated a NOx removal rate significantly greater than less reflective samples cast with gray cement. After carbonation, mixes with 15% fly ash replacement of cement produced the highest NOx removal efficiency for specimens containing the same source of cement.