Removal efficiency of an integrated adsorption/photocatalysis system for reducing low concentrations of nitrogen oxides in microenvironments of museums for cultural relics conservation

Abstract

Nitrogen oxides (NO_x) could pose a threat to the conservation of cultural relics and could also enhance the corrosion induced by other pollutants such as sulphur dioxides and organic acids. The NO_x removal rate was studied through a combination of adsorption onto bamboo charcoal and photocatalysis. The integrated NO_x removal efficiency by both methods was evaluated in both lab and pilot scales. The studies have shown that the direct use of biomass can remove moderate level of NO_x; while higher level of NO_x removal was achieved by using bamboo charcoal carbonized at 520℃. The photocatalytic oxidation of NO_x was found to be well fit with Langmuir–Hinshelwood model. The different carriers of photocatalysis combined with adsorbents were compared, and the optimised process was shown to reduce the nitrogen monoxide and nitrogen dioxide level to 2.76 and 0.68 µg/m³, respectively, in 20% relative humidity (RH). An integrated device was developed, and the results have demonstrated that the combined technologies of photocatalysis and adsorption can have great removal potential for reducing NO_x and therefore in improving the air quality under different RH conditions.