Dechlorination of PCBs in Water Under UV Irradiation and the Relationship Between the Electric Charge Distribution on the Carbon Atom and the Site of Dechlorination Occurrence

Application of quantum chemical descriptors into quantitative structure-property relationship models for prediction of the photolysis half-life of PCBs in water

“…The method to measure the t 1/2 values of PCBs was adopted from the research of Chang et al [20]: an individual PCB congener (1 µg$mL -1 in pure water) was irradiated under a 15 W UV lamp at a wavelength of 254 nm in a separate glass beaker. The determined t 1/2 values for these PCB congeners ranged from 9.0 min to 127.8 min and constituted the training set of the study.…”

“…They found that the reaction rate of PCBs followed apparent first-order kinetics and increased with increasing the TiO 2 concentration. Chang et al [20] studied the photolysis of seven PCBs in water under 254 nm UV irradiation and found that photodechlorination of PCBs in water was similar to that in n-hexane.…”

“…Reportedly, highly chlorinated PCB congeners, particularly those with substitutions at the ortho positions (2,2',6, and 6'), are vulnerable to photochemical attacks [15]. Because all chlorobiphenyls are poorly soluble in water, aqueous photochemistry of PCBs is difficult to be studied [17,18,20,26]. Moor and Pagni found that the photolysis of 4-monochlorobiphenyl in water fitted pseudo-first-order reactions and dechlorination was the principal photoreaction [17].…”

“…However, it is difficult to measure t 1/2 values of PCBs in water because of expensive and time-consuming experiments and use of highly advanced equipment [18,20]. Thus, it is of great importance to develop quantitative structure-property relationship (QSPR) models correlating photolysis process data to physicochemical properties or structural descriptors.…”

“…Many investigations on the photodegradation of PCBs have been reported in recent decades [14][15][16][17][18][19][20]. PCBs are sensitive to ultraviolet (UV) irradiation in aqueous and organic solutions [14][15][16][17]19,21].…”