Characterization of nitrogen-rich biomaterial-derived biochars and their sorption for aromatic compounds

Biochars from nitrogen-rich biomaterials (i.e., α-amylase, chitin and zein) were produced at different temperatures (i.e. 170, 250, 350 and 450 °C) and characterized, and their sorption for phenanthrene, naphthalene and 1-naphthol was investigated. The organic carbon content normalized-sorption coefficient (Koc) of the tested compounds by biochars increased with increasing charring temperature, attributed to the reduction of O-containing polar moieties especially the O-alkyl components, and the newly created aromatic carbon domains. The N-heterocyclic ring structure formed during charring process may enhance π-π interactions between aromatics and the aromatic components in the resulting biochars. However, π-π interactions did not dominate sorption of aromatics by N-rich biochars. Sorption of the tested compounds by N-rich biochars was predominantly controlled by the hydrophobic interactions between these chemicals and the aromatic components in biochars. Both N- and O-containing polar moieties at the biochar surfaces negatively affected their sorption for aromatics.