Concrete blocks nano-modified with zinc oxide (ZnO) for photocatalytic paving: Performance comparison with titanium dioxide (TiO2)

Titanium dioxide (TiO2) has been the semiconductor most used in photocatalytic pavement due to its chemical and physical properties. However, the use of zinc oxide (ZnO) as an alternative material to TiO2 has gained ground in the scenario of heterogeneous photocatalysis, mainly for aqueous medium. This nano-product has characteristics suitable for application in advanced oxidative processes, in addition to having lower market cost compared to TiO2. This study presents the results of the efficiency of NOx degradation of concrete blocks produced with ZnO under different environmental conditions. A comparison of the efficiency of ZnO with TiO2 was also performed, resulting in mathematical models of the photocatalytic cost/performance of nanomaterials. The results showed that ZnO presents lower efficiency when compared to TiO2, being less susceptible to flow rate and more sensitive to UV-A radiation. The application of ZnO as photocatalyst in pavement is only feasible when the market price of ZnO is much lower than that of TiO2. (C) 2020 Elsevier Ltd. All rights reserved.