Structure-dependent photocatalytic degradation of polychlorobiphenyls in a TiO2 aqueous system

Three positional isomers for each polychlorobiphenyl (PCB) homologous group tetra-, penta-, and hexachlorosubsubstituted were irradiated in a TiO2 (anatase) semiconductor aqueous suspension. Parent PCB disappearance was studied as a function of irradiation time, and a correlation between isomer substitution pattern and the photodegradative behavior was shown. In each group, the slowest disappearance trend was exhibited by the isomer with unsubstituted ortho positions, thereby capable of adapting into a planar structural configuration with minimum (estimated) energy requirement. In general, photodegradation rate increased with increasing degree of ortho chlorosubstitution.