Experimental and density functional theory calculation study on the NO2 adsorption and reduction by KOH activated biochar

Abstract

Biochar prepared from waste biomass as an adsorption and reduction material can effectively decrease decrease nitrogen dioxide (NO2) emissions. This work aims to select suitable materials to prepare biochar and improve its ability to adsorb and reduce NO2. In this study, the process of adsorption and reduction of NO2 by biochar and the effect of KOH activation on these reactions are studied by using fixed-bed reactor and density functional theory calculation. Experimental results indicate a positive correlation between the adsorption and reduction capabilities of biochar for NO2 and its specific surface area and surface oxygen groups. The biochar sample prepared by pyrolysis at 800 ℃ with the addition of 3 wt% KOH solution exhibits the highest adsorption capacity, likely due to the catalytic role of potassium (K) in the adsorption-reduction reaction. It is worth noting that the theoretical calculation results confirm this point. The K atom primarily facilitates the breaking of the N-O bond in NO2 and the desorption of the NO molecule on biochar through van der Waals forces, thereby lowering the reaction energy barrier. Thermodynamic and kinetic analyses further confirm these findings. This study has a new understanding of the mechanism of NO2 adsorption and reduction of by KOH activated biochar, which provides experimental basis and theoretical guidance for the application of this technology.