Polychlorinated biphenyl (PCB) partition equilibrium between St. Lawrence River sediments and supercritical fluids

Abstract

New reliable and extensive polychlorinated biphenyl (PCB) partition equilibrium data between real world PCB contaminated St. Lawrence River sediments (SLRS) and two supercritical fluids (SCFs), scCO 2 and scCO 2/5 mol% MeOH, are presented. Three real world SLRS samples with similar physical properties and PCB congener distribution patterns but different PCB concentration levels were used to conduct experiments at 313, 323, and 333 K and SCF densities from 5.5 to 18 mol/l. The experimental results are presented as partition coefficients, K, for 16 PCB congeners and for the total PCBs in the SLRS. The presence of methanol in the SC phase increases PCB desorption, as expected. Two partition equilibrium models are employed to correlate these data sets for each of the two SCFs used. The effects of SCF density on K and the parameters of the models are presented for each PCB congener in both systems of scCO 2 and scCO 2/MeOH. Preferential desorption is found among the PCB congeners and it is suggested that the partition coefficients increase roughly in the order of PCB molar weight. These models can be used in the design of large scale PCB desorption equipment.