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 describe d 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 cons tants obtained were found to be dependent on both the number and the p ositions of the chlorines. A general increase in the dose constant was observed with increasing chlorine number. Chlorine substitution in th e para and meta position increases the dose constant while substitutio n in the ortho position decreases it. Dose constant trends follow the energy level of the lowest unoccupied molecular orbital. Previously un reported degradation products consisting of 2-propanol-substituted pol ychlorinated biphenyls are characterized. Mass balance information is incomplete for some congeners. Based upon experiments using a C-14-lab eled tetrachlorobiphenyl, degradation products are in nonvolatile or s emivolatile constituents.