Modelling an amorphous biochar structure using classical molecular dynamics simulations

Abstract

Biochar (BC) is a highly porous carbonaceous material with excellent adsorbent properties. The surface properties of BC can be modified to enhance the efficiency of adsorption of specific compounds. However, experimental studies into the adsorbate adsorbent interactions remain tedious, expensive and time-consuming. Several in-silico studies into these interactions are available using graphitic models and single molecules. In this work computational modelling of amorphous BC in its natural form is done using an amorphous BC model developed through pyrolysis-quenching of graphite. Classical molecular dynamics with a ReaxFF interatomic potential is used to computationally develop the amorphous BC model. The resulting structure was then validated visually, through simulated TEM as well as by analyzing the calculated FTIR spectrum of the model, while the amorphicity was established by a 3D Radial Distribution Function of the carbon skeleton. The in-silico BC model was deemed to be an accurate representation of amorphous BC. The amorphous BC structure that we have developed in this study is a very close representation of the BC found in nature and hence the adsorption studies that were subsequently carried out is also more accurate than existing studies on the adsorption of various chemical species onto BC.