Efficient Removal of Ammonia by Hierarchically Porous Carbons from a CO₂ Capture Process

The amine-based post-combustion carbon capture process is one of the most efficient methods for treating large-scale CO₂, but it produces hazardous products due to chemical transition and degradation of the absorbents. In this study, carbon-based materials were used as adsorbents for the removal of NH₃, and their adsorption capacities, adsorption rates, and stabilities were examined by comparing commercial activated carbon (AC) with hierarchically porous carbon (HPC). HPC-Step4 possessed a higher number of total acid sites, resulting in higher NH₃ adsorption compared to AC. Despite the similar porosity, HPC-Step4 exhibited a higher adsorption rate constant and the improved kinetics was attributed to its increased portion of mesopores, enhancing the diffusion rate of the adsorbate. Furthermore, HPC-Step4 exhibited better reaction stability than AC.