Acid hydrolysis lignin as a sorbent for naphthalene

Lignin, a major polymeric constituent of woody plant tissue, is an abundant source of natural organic matter available as a waste product from the pul p and paper and the fuel ethanol industries. In this study, the sorptive ca pacity of acid hydrolysis lignin for naphthalene, a representative nonpolar hydrophobic organic compound (HOC), was investigated. When powdered lignin is mixed with distilled water, dissolved and/or colloidal organic matter l eaches into the aqueous phase imparting a cloudy yellowish colour. A washin g and filtering protocol was developed for pretreating the lignin employed in the sorption studies. Results from batch sorption experiments showed tha t acid hydrolysis lignin has a strong affinity for naphthalene. The Freundl ich isotherm coefficients obtained indicate that the sorption isotherm for naphthalene on hydrolysis lignin is nearly linear. A modified Freundlich eq uation was employed in order to compare sorption data for HOCs on lignin an d activated carbon through the use of unit equivalent coefficients. The res ults presented in this research and in the literature suggest that the two sorbents are comparable in terms of sorption coefficients. It was determine d that acid hydrolysis lignin is unsuitable for use in a packed bed since p umping a naphthalene solution through a column packed with lignin caused th e wet lignin to become significantly hardened over time, resulting in a lar ge pressure drop across the system.