Sorption of Polycyclic Aromatic Hydrocarbons (PAHs) to Lignin: Effects of Hydrophobicity and Temperature

The study of the sorption of contaminants to lignin is significant for understanding the migration of contaminants in the environment as well as developing low cost sorbent. In this study, sorption of three polycyclic aromatic hydrocarbons (PAHs), naphthalene, acenaphthene and phenanthrene, to lignin was investigated. Sorption isotherms were well described by both linear and Freundlich sorption models. Sorption coefficients of PAHs to lignin from water obtained from regression of both linear model (K (d)) and Freundlich model (K (f)) were highly positively correlated with hydrophobicity of PAHs. The amorphous structure of lignin provided sufficient sorption domain for partitioning of PAHs, and the attraction between PAHs molecules and aromatic fractions in lignin via pi-pi electron-donor-acceptor (pi-pi EDA) interaction is hypothesized to provide a strong sorption force. Thermodynamic modeling revealed that sorption of PAHs to lignin was a spontaneous and exothermic process.