Abstract
Pyrogenic carbon is widespread in soil due to wildfires, soot deposition, and intentional amendment of pyrolyzed waste biomass (biochar). Interactions between engineered carbon nanoparticles and natural pyrogenic carbon (char) are unknown. This study first employed transmission electron microscopy (TEM) and X-ray diffraction (XRD) to interpret the superstructure composing aqueous fullerene C60 nanoparticles prepared by prolonged stirring of commercial fullerite in water (nC60-stir). The nC60-stir was a superstructure composed of face-centered cubic (fcc) close-packing of near-spherical C60 superatoms. The nC60-stir superstructure (≈100 nm) reproducibly disintegrated pecan shell biochar pellets (2 mm) made at 700 °C into a stable and homogeneous aqueous colloidal (<100 nm) suspension. The amorphous carbon structure of biochar was preserved after the disintegration, which only occurred above the weight ratio of 30,000 biochar to nC60-stir. Favorable hydrophobic surface interactions between nC60-stir and 700 °C biochar likely disrupted van der Waals forces holding together the amorphous carbon units of biochar and C60 packing in the nC60 superstructure.