Study on a Dechlorination of PCBs using UV Irradiation

Polychlorinated biphenyls (PCBs) are reduced to biphenyls in alkaline 2-propanol when irradiated with UV rays. This process brings down the PCBs concentration to below 0.5 ppm and produces sodium chloride (NaCl) as a by-product. In order to develop suitable technology for removing PCBs using this principle it is important to study factors that influence this reaction. In this paper, we investigated the effects of UV irradiation density, reaction temperature, UV wavelength, concentrations of NaOH, H2O and trichlorobenzenes (TCBz) . It was particularly important to study the effects of TCBz. This study established PCBs decomposition to be independent of TCBz concentration, with TCBz concentration less than PCBs. The decomposition efficiency was also found to be independent of UV irradiation density and solution temperature, between 50°C and 70°C. The effective UV wavelength for reductive dechlorination of PCBs was between 254 and 270 mm. The moisture surrounding the solution was saturated with NaOH to suppress the effect of water in preventing the reaction.