Removal of polycyclic aromatic hydrocarbons from aqueous solution using plant residue materials as a biosorbent

To elucidate biosorption mechanism and removal efficiency of plant residues as a biosorbent to abate polycyclic aromatic hydrocarbons (PAHs) in wastewater, sorption of PAHs onto wood chips (WC), ryegrass roots (RR), orange peels (OP), bamboo leaves (BL), and pine needles (PN) were investigated. The structural characterization of the biosorbents was analyzed by elemental composition, BET-N(2) surface area, and Fourier transform infrared spectroscopy. PAHs sorption to the selected biosorbents were compared and correlated with their structures. Biosorption isotherms fit well with Freundlich equation and the mechanism was dominated by partition process. The magnitude of phenanthrene partition coefficients (K(d)) followed the order of PN > BL > OP > RR > WC, ranged from 2484 ± 24.24 to 5306 ± 92.49 L/kg. Except the WC sample, the K(d) values were negatively correlated with sugar content, polar index [(N+O)/C] of the biosorbents, while the aromatic component exhibited positive effects. For a given biosorbent of bamboo leaves, the carbon-normalized partition coefficients (K(oc)) were linearly correlated with octanol-water partition coefficients (K(ow)) of PAHs, i.e., logK(oc) = 1.16 log K(ow)-1.21. The structure-effect relationship provides a reference to select and modify plant residues as a biosorbent with high efficiency to tackle organic pollutants.