Sorption of PAHs by Aspen Wood Fibers as Affected by Chemical Alterations

Sorption and desorption experiments for phenanthrene and pyrene, using untreated (UTR) and treated (bleaching and hydrolysis) aspen wood fibers, were examined to understand their sorption mechanisms. The wood was characterized by elemental and porosity analysis, solid-state ¹³C NMR, and diffuse reflectance infrared Fourier transform spectroscopy. Bleaching removed aromatic components, yielding the highest polarity and increased porosity, whereas hydrolysis removed a large percentage of hemicellulose and parts of amorphous cellulose, producing a matrix with more aromatic moieties, lower polarity, and higher porosity than that of the UTR wood fibers. All isotherms fitted well to the Freundlich equation and the N values had a decreasing trend from bleached (BL), UTR, low-temperature hydrolyzed to high-temperature hydrolyzed (HHY) wood fibers. BL fibers had the lowest sorption capacity (K_OC) for both phenanthrene and pyrene. HHY had the highest K_OC because of its high aromatic carbon content and low polarity. The results suggest that aromatic moieties and polarity of wood fibers play significant roles in polycyclic aromatic hydrocarbon (PAHs) sorption and desorption. Thus, both aromatic components and polarity should be considered when predicting the PAHs sorption/desorption by aspen wood fibers. This study demonstrated that aspen wood fibers are a potential sorbent for PAHs and that chemical modifications of the wood matrix can effectively increase its sorption efficiency. These results may have implications for the treatment of stormwater runoff and other PAH-contaminated liquids.