Effect of KOH-N2/CO/air activation on the performance of coconut shell activated carbon for low temperature NH3 removal NO

Abstract

This study investigates the effects of different combinations of potassium hydroxide (KOH)–nitrogen (N₂₎/carbon monoxide (CO)/air activation on the low-temperature ammonia (NH₃) removal NO performance of coconut shell-activated carbon. KOH–N₂-combined activation resulted in expanded pores of activated carbon, while high temperatures caused structural collapse. While increasing the activation temperature induced larger average pore sizes, introducing nitrogen-containing functional groups on the surface positively affected the NO conversion rate. Furthermore, while KOH–CO₂-combined activation yielded activated carbon with denser and more ordered pore structures upon increasing activation temperature, a relatively large specific surface area and total pore volume were also observed. Introducing functional groups such as C = C on the surface yielded a higher overall NO conversion rate. Although KOH–air activation resulted in developed porous structures, some pore sizes were blocked, thereby yielding a smaller specific surface area. Nevertheless, introducing nitrogen-containing functional groups contributed to an overall increase in the NO conversion rate. Orthogonal experimental analysis revealed that activation time significantly impacted the physical activation process of KOH-activated carbon, followed by activation temperature, with activation gas minimally affecting the activated carbon structure and NO conversion rate. Notably, the optimal activation conditions included 1-h activated carbon activation in 3 mol/L of KOH, followed by 1-h CO₂ activation at 150℃.