Photodegradation of five strategically selected PCBs was carried out in acetonitrile/water 80:20. Quantum chemical calculations reveal that PCBs without any chlorine on ortho-positions are closer to be planar, while PCBs with at least one chlorine atoms at the ortho-positions causes the two benzene rings to be nearly perpendicular. Light-induced degradation of planar PCBs is much slower than the perpendicular ones. The use of nano-TiO(2) speeds up the degradation of the planar PCBs, but slows down the degradation of the non-planar ones. The use of H(2)O(2) speeds up the degradation of planar PCBs greatly (by >20 times), but has little effect on non-planar ones except 2,3,5,6-TCB. The relative photodegradation rate is: 2,2',4,4'-TCB > 2,3,5,6-TCB > 2,6-DCB ≈ 3,3',4,4'-TCB > 3,4',5-TCB. The use of H(2)O(2) in combination with sunlight irradiation could be an efficient and "green" technology for PCB remediation.
Keywords: H2O2; PCBs; TiO2; dechlorination; photodegradation.