GAMMA-RAY DESTRUCTION OF INDIVIDUAL PCB CONGENERS IN NEUTRAL 2-PROPANOL

The radiolytic degradation of 25 PCB congeners from nine homologs was investigated in neutral aerated 2-propanol using spent nuclear fuel as the gamma-ray source. Radiolytic degradation is conveniently described in terms of a pseudo-first-order rate constant expressed in terms of dose, rather than time, and referred to as a dose constant. Dose constants obtained were found to be dependent on both the number and the positions of the chlorines. A general increase in the dose constant was observed with increasing chlorine number. Chlorine substitution in the para and meta position increases the dose constant while substitution in the ortho position decreases it. Dose constant trends follow the energy level of the lowest unoccupied molecular orbital. Previously unreported degradation products consisting of 2-propanol-substituted polychlorinated biphenyls are characterized. Mass balance information is incomplete for some congeners. Based upon experiments using a C-14-labeled tetrachlorobiphenyl, degradation products are in nonvolatile or semivolatile constituents.