Kinetics of hydrophobic organic contaminant extraction from sediment by granular activated carbon

Ex situ solid phase extraction with granular activated carbon (GAC) is a promising technique to remediate contaminated sediments. The methods' efficiency depends on the rate by which contaminants are transferred from the sediment to the surface of GAG. Here, we derive kinetic parameters for extraction of polycyclic aromatic hydrocarbons (PAH) from sediment by GAG, using a first-order multi-compartment kinetic model. The parameters were obtained by modeling sediment-GAG exchange kinetic data following a tiered model calibration approach. First, parameters for PAH desorption from sediment were calibrated using data from systems with 50% (by weight) GAG acting as an infinite sink. Second, the estimated parameters were used as fixed input to obtain GAG uptake kinetic parameters in sediment slurries with 4% GAG, representing the ex situ remediation scenario. PAH uptake rate constants (k(GAC) by GAG ranged from 0.44 to 0.0005 d(-1), whereas GAG sorption coefficients (K-GAC ranged from 10(5.57) to 10(8.57) L kg(-1). These values are the first provided for GAG in the presence of sediment and show that ex situ extraction with GAG is sufficiently fast and effective to reduce the risks of the most available PAHs among those studied, such as fluorene, phenanthrene and anthracene. (C) 2013 Elsevier Ltd. All rights reserved.