Photocatalytic NO_xdegradation of concrete surface layers intermixed and spray-coated with nano-TiO₂: Influence of experimental factors

However, under real-life service, various environmental factors will significantly influence their photocatalytic performance. In this study, the photocatalytic NOxconversion of two sets of concrete surface layers (intermixed and spray-coated with nano-TiO2) was investigated and compared under different NO flow rates, initial NO concentrations, ultraviolet (UV) light intensities, light sources and relative humidity (RH) conditions. In addition, the abrasion resistance of all the samples was examined. The results showed that the TiO2spray-coated samples (SP) outperformed the 5% TiO2-intermixed samples with respect to NOxremoval efficiency under all the investigated conditions. Both the NO flow rate and initial NO concentration had a positive impact on the NOxremoval rate but a negative influence on the NOxremoval ratio. An increase in photocatalytic NOxremoval rate and NOxremoval ratio was attained by an increase in UV light intensity. Whereas, the NOxremoval efficiency first increased, reached a peak, and then decreased with increasing RH. It was found that the most effective light source for photocatalytic NOxremoval was UV-A, but Solar light (SL) irradiation resulted in a comparable NOxremoval. Moreover, the SP samples harboured robust resistance to abrading. The findings from this study would provide the basis for effectively evaluating the NOxremoval performance of concrete surface layers under atmospheric conditions.