Equilibrium and kinetic modeling of contaminant immobilization by activated carbon amended to sediments in the field Magdalena I. Rakowska a,* , Darya Kupryianchyk b,d , Albert A. Koelmans b,c , Tim Grotenhuis a , Huub H.M. Rijnaarts a a Subdepartment of Environmental Technology, Department of Agrotechnology and Food Science, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands b Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands c IMARES e Institute for Marine Resources & Ecosystem Studies, Wageningen UR, P.O. Box 68, 1970 AB IJmuiden, The Netherlands d Department of Environmental Technology, Norwegian Geotechnical Institute, 0806 Oslo, Norway article info Article history: Received 4 May 2014 Received in revised form 28 July 2014 Accepted 30 July 2014 Available online 7 August 2014 Keywords: Sediment remediation Activated carbon Hydrophobic compounds Passive sampling Kinetics abstract Addition of activated carbons (AC) to polluted sediments and soils is an attractive reme- diation technique aiming at reducing pore water concentrations of hydrophobic organic contaminants (HOCs). In this study, we present (pseudo-)equilibrium as well as kinetic parameters for sorption of a series of PAHs and PCBs to powdered and granular activated carbons (AC) after three different sediment treatments: sediment mixed with powdered AC (PAC), sediment mixed with granular AC (GAC), and addition of GAC followed by 2 d mixing and subsequent removal (‘sediment stripping’). Remediation efficiency was assessed by quantifying fluxes of PAHs towards SPME passive samplers inserted in the sediment top layer, which showed that the efficiency decreased in the order of PAC > GAC stripping > GAC addition. Sorption was very strong to PAC, with Log K AC (L/kg) values up to 10.5. Log K AC values for GAC ranged from 6.3e7.1 and 4.8e6.2 for PAHs and PCBs, respec- tively. Log K AC values for GAC in the stripped sediment were 7.4e8.6 and 5.8e7.7 for PAH and PCB. Apparent first order adsorption rate constants for GAC (k GAC ) in the stripping scenario were calculated with a first-order kinetic model and ranged from 1.6 Â 10 À2 (PHE) to 1.7 Â 10 À5 d À1 (InP). Sorption affinity parameters did not change within 9 months post treatment, confirming the longer term effectiveness of AC in field applications for PAC and GAC. © 2014 Published by Elsevier Ltd. * Corresponding author. Tel.: þ31 (0)317 83997. E-mail addresses: magdalena.rakowska@wur.nl, m.iwona.rakowska@gmail.com (M.I. Rakowska). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/watres water research 67 (2014) 96 e104 http://dx.doi.org/10.1016/j.watres.2014.07.046 0043-1354/© 2014 Published by Elsevier Ltd.