Combined decontamination processes for wastes containing PCBs

Dehalogenation of polychlorinated biphenyls (PCB) by nucleofile reactants at the presence of ionic liquids and under application of microwaves

“…The choice of the nucleophilic reactant composition was influenced by our previous experimental results (Kastanek, 2005) and by our experience with reaction rates of the decomposition of the lower chlorinated PCB congeners. Contaminated oil (sample K-0) in 30mL quantity was poured into the reactor which was equipped with the condenser and magnetic stirrer and the reactor was placed on a hot plate.…”

“…Powdered KOH (approximately 15% moisture) was added in amounts 1.5g, 3g, and 4.5g. The constant ratio KOH/ PEG = 0.15 was selected based on the results of our previous work (Kastanek, 2005). The sample was maintained at the temperature 125-145 o C for 30, 60, and 90 minutes.…”

“…It seems that the reaction does not show regio-selectivity, nevertheless congeners with higher number of chlorine atoms (ideally with 6-7 atoms) are degraded preferentially. Both laboratory and pilot plant tests performed with less chlorinated PCBs differ significantly (Kastanek, 2005) from the original data (Brunelle et al,1985)) and indicate that the reaction rate of congeners with three and four chlorine atoms is much lower (Sabata et al,1993). This is important for example for decontamination of transformer oils in Czech Republic, where the technical mixture DELOR 103, containing mainly less chlorinated congeners was used widely in dielectric fluids.…”

“…In years 1996-2002, pilot plant and industrial scale testing of selected alternative methods of PCBs removal from various media was undertaken in Czech Republic. Results of the tests were summed up by the authors of this paper (Kastanek, 2005). Industrial tests performed with more of 500kg of contaminated oils in a batch showed that the known nucleophilic methods (KPEG), in contrast with the published data (Brunelle et al, 1985), destructed PCBs in the oils very slowly, even when high temperatures (around 160 o C) were used.…”

“…This is important for example for decontamination of transformer oils in Czech Republic, where the technical mixture DELOR 103, containing mainly less chlorinated congeners was used widely in dielectric fluids. Treatment of less chlorinated PCBs by the KPEG method requires large volumes of reagents and temperatures much higher than 100 o C in the range of 145-170 o C (Kastanek, 2005). However at these temperatures we are already crossing the line of safe work environment because molecular hydrogen is being released and the reaction is very difficult to be controlled.…”