NOx sequestration by calcium aluminate cementitious materials

This study quantifies NOx uptake efficiency and explores NOx binding mechanisms in calcium aluminate cementitious (CAC) materials. 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 similar to 50% of converted NOx resists releasing back into the environment via dissolution. Compared to previously studied ordinary portland cement (OPC) materials, CAC increases NOx uptake capacity and demonstrates a more permanent NOx binding, potentially mitigating concerns related to the release of previously bound N-species in OPC. Examination of the interaction between NOx and a synthetic pure aluminum-bearing phase shows that the permanent NOx uptake in CAC could be largely attributed to the chemical binding of converted NOx within aluminum-bearing phases.

Automated summary

This study quantifies NOx uptake efficiency and explores binding mechanisms in CAC materials. Unmodified CAC utilizes surface-related heterogeneous reactions for NOx binding, while TiO2-modified CAC increases NOx uptake through photocatalytic reactions.