Relative resistance of positional isomers of polychlorinated biphenyls toward reductive dechlorination by zerovalent iron in subcritical water

Relative resistance of positional isomers within the same homologue of poly chlorinated biphenyls (PCBs) was studied by comparing the reduction efficie ncies (REs) of these isomers by 100-mesh zerovalent iron in subcritical wat er at 250 degrees C and 10 MPa. The REs far meta and para isomers were foun d to be significantly higher than that of the ortho's. These results reveal ed that Variation in relative resistance of the positional isomers to reduc tive dechlorination does exist, and the order increases from para to meta t o ortho substituents. This variation in relative resistance to reduction is correlated with the lowest unoccupied molecular orbital (LUMO) energy of i ndividual PCB congeners. A model based on the empirical relative resistance of the PCBs to reductive dechlorination is developed, and an equation is e stablished to predict the efficiency of a reductive dechlorination system t hat employs zerovalent iran and pressurized hot water.