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

• Sediment stripping with GAC effectively reduces the risk of fluorene, phenanthrene and anthracene within a few days.
• GAC uptake kinetic parameters in mixed sediment-GAC systems are determined with a tiered first-order model approach.
• Rate and affinity constants for PAH adsorption to GAC correlate with PAH hydrophobicity.

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 GAC. Here, we derive kinetic parameters for extraction of polycyclic aromatic hydrocarbons (PAH) from sediment by GAC, using a first-order multi-compartment kinetic model. The parameters were obtained by modeling sediment-GAC 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) GAC acting as an infinite sink. Second, the estimated parameters were used as fixed input to obtain GAC uptake kinetic parameters in sediment slurries with 4% GAC, representing the ex situ remediation scenario. PAH uptake rate constants (kGAC) by GAC ranged from 0.44 to 0.0005 d−1, whereas GAC sorption coefficients (KGAC) ranged from 105.57 to 108.57 L kg−1. These values are the first provided for GAC in the presence of sediment and show that ex situ extraction with GAC is sufficiently fast and effective to reduce the risks of the most available PAHs among those studied, such as fluorene, phenanthrene and anthracene.

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