Chitosan-Doped TiO2 Functionalized Asphalt Mixtures for NO2 Mitigation Under High Pollution Levels

Abstract

Improving air quality is a significant environmental challenge. This research explored the potential of asphalt mixtures functionalized with a chitosan–TiO2 composite (CS-TiO2) to reduce high NO2 concentrations and improve durability. For the assessment of the photocatalytic efficiency of the new CS-TiO2 composite, a low-cost reactor adapted to accommodate asphalt Marshall-type specimens and high pollutant concentrations encompassing a passive sampling module was developed. The CS-TiO2 was synthesized using a wet impregnation method at a concentration of 2%, and asphalt mixtures were treated with aqueous solutions of the photocatalysts at 2.5 g/m2 and 5.0 g/m2. Laboratory tests using the photocatalytic reactor and passive sampling of NO2 revealed pollutant reductions of 21% with TiO2 and 28% with CS-TiO2. CS-TiO2 achieved 15% efficiency in visible light, reducing NO2 levels and offering UV protection to the asphalt mixtures. Additionally, the chitosan improved the photocatalyst’s adhesion by about 18%, as confirmed by tape test results, suggesting enhanced durability on pavement surfaces. The results achieved showcase the relevance of the proposed methodological improvements for supporting further research.