Enhanced NOx sequestration by aluminate-rich cement
We have demonstrated that the TiO2-modified calcium aluminate cement (CAC)-based materials exhibit a more permanent NOx binding compared to portland cement (OPC)-based ones, potentially mitigating concerns related to the release of previously bound N-species in OPC. Comparison between unmodified and TiO2-modified CAC separates intrinsic NOx binding mechanisms from those related to photocatalysis. Attributed to surface-related heterogeneous reactions, the NOx binding occurs in unmodified CAC at nitrite-to-nitrate ratio of 1: 1.3 and can be increased with surface area. The photocatalytic reactions in TiO2-modified CAC increase NOx uptake, and ~50% of converted NOx resists releasing back into the environment via dissolution.