A new approach for complete pore size distributions and regime-specific total pore volume determinations of biochars

Knowledge of biochar surface characteristics is critical to understanding its performance in many applications. Biochars often contain a significant amount of micropores and ultramicropores, which makes analyzing the specific surface area (SSA) of these materials via N2 adsorption at 77K (BET) unreliable due to kinetic restrictions at cryogenic temperatures. Because of this, alternative and more reliable methods must be developed in order to elucidate structure-performance relationships.  Here we present a new  method for combining data from multiple experiments to generate a complete pore size distribution (0.36 to 500,000 nm).  A 2D non-local density functional theory model is used to simultaneously fit CO2 (273 K) and N2 (77 K) adsorption isotherms covering the range from of 0.36 to 30 nm while mercury intrusion porosimetry is used for larger pore sizes, completing the distribution up to 500,000 nm.  In addition to pore size distributions, regime specific total pore volumes can also be determined. This presentation will cover method details and will share data generated from the analysis of a series of balsam fir biochars produced at various highest thermal treatment temperatures. 

Dr Brian Barry
Chemistry & Materials Science Leader
Natural Resources Research Institute, Duluth, MN, United States