NOx de-pollution by hardened concrete and the influence of activated charcoal additions

Abstract The atmospheric pollution by nitrogen oxides affects the health of millions of people located in urban areas. Our work demonstrates that, even in the absence of photocatalysts, concrete walls can strongly absorb NO 2 and limit the intensity of pollution peaks. Our results show that concretes can continuously absorb a significant fraction of NO 2 from the surrounding atmosphere over long periods, probably due to a reaction with strongly alkaline cement hydrates. Moreover, the introduction of a small amount of activated charcoal into the concrete mix can significantly enhance and prolong this NO 2 absorption without greatly increasing total porosity or decreasing strength. We hypothesize that the NO 2 is adsorbed irreversibly by a neutralization reaction with the alkaline aqueous solution covering the surfaces of the hydrates and the activated charcoal. Simple calculations suggest that walls made of activated charcoal concrete could ameliorate the problem of NO 2 pollution peaks in road tunnels and parking garages.